Docs: fix typo in deeplinking docs
Docs: fix typo in deeplinking docs

Summary:
Just a small typo in the docs, the suggested code uses a variable that doesn't exist and leads to a compile error.
Closes https://github.com/facebook/react-native/pull/15196

Differential Revision: D5490031

Pulled By: javache

fbshipit-source-id: cb1e15b22f0d8f282afb3943fb4f5d0dc5dad9e7

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