Improve spacing in polyfill error messages
Improve spacing in polyfill error messages

Summary:
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Noticed a lack of spacing in the following error message:

```
In this environment the sources for assign MUST be an object.This error is a performance optimization and not spec compliant.
TypeError: In this environment the sources for assign MUST be an object.This error is a performance optimization and not spec compliant.
    at Object.assign (http://localhost:8081/index.android.bundle?platform=android&dev=true&hot=false&minify=false:230:15)
    at http://localhost:8081/index.android.bundle?platform=android&dev=true&hot=false&minify=false:134559:46
    at Array.map (native)
    at GridComponent._callee$ (http://localhost:8081/index.android.bundle?platform=android&dev=true&hot=false&minify=false:134554:58)
    at tryCatch (http://localhost:8081/index.android.bundle?platform=android&dev=true&hot=false&minify=false:7388:40)
    at Generator.invoke [as _invoke] (http://localhost:8081/index.android.bundle?platform=android&dev=true&hot=false&minify=false:7576:22)
    at Generator.prototype.(anonymous function) [as next] (http://localhost:8081/index.android.bundle?platform=android&dev=true&hot=false&minify=false:7413:21)
    at tryCatch (http://localhost:8081/index.android.bundle?platform=android&dev=true&hot=false&minify=false:7388:40)
    at invoke (http://localhost:8081/index.android.bundle?platform=android&dev=true&hot=false&minify=false:7446:20)
    at http://localhost:8081/index.android.bundle?platform=android&dev=true&hot=false&minify=false:7476:11
```

Tested by updating the message locally in `/path/to/rn-project/node_modules/react-native/packager/src/Resolver/polyfills/Object.es6.js`.
Closes https://github.com/facebook/react-native/pull/15166

Differential Revision: D5481475

Pulled By: javache

fbshipit-source-id: f3e4e482a8ee61d52e8c3e0c5f038b1109bd1113

exponent/react-native,janicduplessis/react-native,negativetwelve/react-native,farazs/react-native,facebook/react-native,exponentjs/react-native,rickbeerendonk/react-native,exponent/react-native,jevakallio/react-native,rickbeerendonk/react-native,janicduplessis/react-native,makadaw/react-native,myntra/react-native,Bhullnatik/react-native,kesha-antonov/react-native,negativetwelve/react-native,farazs/react-native,makadaw/react-native,exponentjs/react-native,javache/react-native,facebook/react-native,farazs/react-native,negativetwelve/react-native,dikaiosune/react-native,negativetwelve/react-native,hoastoolshop/react-native,exponentjs/react-native,kesha-antonov/react-native,pandiaraj44/react-native,rickbeerendonk/react-native,cdlewis/react-native,jevakallio/react-native,rickbeerendonk/react-native,hoangpham95/react-native,myntra/react-native,rickbeerendonk/react-native,negativetwelve/react-native,farazs/react-native,pandiaraj44/react-native,rickbeerendonk/react-native,exponent/react-native,hoangpham95/react-native,makadaw/react-native,hammerandchisel/react-native,hammerandchisel/react-native,pandiaraj44/react-native,arthuralee/react-native,janicduplessis/react-native,negativetwelve/react-native,kesha-antonov/react-native,hoangpham95/react-native,facebook/react-native,janicduplessis/react-native,arthuralee/react-native,kesha-antonov/react-native,ptmt/react-native-macos,frantic/react-native,pandiaraj44/react-native,exponent/react-native,farazs/react-native,hammerandchisel/react-native,hammerandchisel/react-native,hoangpham95/react-native,farazs/react-native,dikaiosune/react-native,rickbeerendonk/react-native,janicduplessis/react-native,hoastoolshop/react-native,hoastoolshop/react-native,Bhullnatik/react-native,facebook/react-native,ptmt/react-native-macos,jevakallio/react-native,exponentjs/react-native,exponentjs/react-native,hoastoolshop/react-native,kesha-antonov/react-native,cdlewis/react-native,cdlewis/react-native,negativetwelve/react-native,makadaw/react-native,makadaw/react-native,rickbeerendonk/react-native,ptmt/react-native-macos,exponent/react-native,facebook/react-native,facebook/react-native,hoastoolshop/react-native,hoangpham95/react-native,cdlewis/react-native,pandiaraj44/react-native,kesha-antonov/react-native,cdlewis/react-native,farazs/react-native,makadaw/react-native,facebook/react-native,pandiaraj44/react-native,myntra/react-native,myntra/react-native,hoangpham95/react-native,myntra/react-native,kesha-antonov/react-native,cdlewis/react-native,negativetwelve/react-native,Bhullnatik/react-native,janicduplessis/react-native,dikaiosune/react-native,kesha-antonov/react-native,Bhullnatik/react-native,hammerandchisel/react-native,hoastoolshop/react-native,dikaiosune/react-native,hammerandchisel/react-native,javache/react-native,hoangpham95/react-native,exponentjs/react-native,kesha-antonov/react-native,dikaiosune/react-native,exponentjs/react-native,makadaw/react-native,javache/react-native,ptmt/react-native-macos,myntra/react-native,javache/react-native,myntra/react-native,rickbeerendonk/react-native,janicduplessis/react-native,Bhullnatik/react-native,hoangpham95/react-native,exponentjs/react-native,hoastoolshop/react-native,javache/react-native,farazs/react-native,hoastoolshop/react-native,makadaw/react-native,hammerandchisel/react-native,farazs/react-native,pandiaraj44/react-native,facebook/react-native,jevakallio/react-native,negativetwelve/react-native,myntra/react-native,myntra/react-native,cdlewis/react-native,javache/react-native,ptmt/react-native-macos,jevakallio/react-native,arthuralee/react-native,ptmt/react-native-macos,frantic/react-native,javache/react-native,exponent/react-native,ptmt/react-native-macos,Bhullnatik/react-native,facebook/react-native,hammerandchisel/react-native,cdlewis/react-native,ptmt/react-native-macos,cdlewis/react-native,exponent/react-native,Bhullnatik/react-native,jevakallio/react-native,frantic/react-native,jevakallio/react-native,Bhullnatik/react-native,arthuralee/react-native,exponent/react-native,frantic/react-native,frantic/react-native,makadaw/react-native,dikaiosune/react-native,javache/react-native,dikaiosune/react-native,arthuralee/react-native,janicduplessis/react-native,dikaiosune/react-native,jevakallio/react-native,pandiaraj44/react-native,javache/react-native,jevakallio/react-native