Fix Skylint warnings in rn_defs.bzl.
Fix Skylint warnings in rn_defs.bzl.

Summary: Instead of ignoring the linter, it's better to fix the warnings :)

Differential Revision: D13512033

fbshipit-source-id: a3db1417ddfde2e05a0c03c204f3627cc15c5a2d

exponent/react-native,javache/react-native,javache/react-native,facebook/react-native,myntra/react-native,facebook/react-native,hoangpham95/react-native,hammerandchisel/react-native,hoangpham95/react-native,javache/react-native,janicduplessis/react-native,exponentjs/react-native,janicduplessis/react-native,javache/react-native,arthuralee/react-native,exponentjs/react-native,pandiaraj44/react-native,myntra/react-native,hoangpham95/react-native,janicduplessis/react-native,hoangpham95/react-native,exponent/react-native,exponent/react-native,exponent/react-native,hammerandchisel/react-native,exponent/react-native,hammerandchisel/react-native,exponent/react-native,janicduplessis/react-native,javache/react-native,pandiaraj44/react-native,janicduplessis/react-native,hammerandchisel/react-native,myntra/react-native,facebook/react-native,myntra/react-native,exponentjs/react-native,pandiaraj44/react-native,pandiaraj44/react-native,hammerandchisel/react-native,exponentjs/react-native,arthuralee/react-native,exponent/react-native,hoangpham95/react-native,hoangpham95/react-native,pandiaraj44/react-native,javache/react-native,facebook/react-native,javache/react-native,hoangpham95/react-native,myntra/react-native,myntra/react-native,javache/react-native,arthuralee/react-native,pandiaraj44/react-native,exponentjs/react-native,exponentjs/react-native,hammerandchisel/react-native,facebook/react-native,myntra/react-native,janicduplessis/react-native,pandiaraj44/react-native,arthuralee/react-native,janicduplessis/react-native,exponent/react-native,facebook/react-native,facebook/react-native,hammerandchisel/react-native,pandiaraj44/react-native,hoangpham95/react-native,facebook/react-native,arthuralee/react-native,javache/react-native,exponentjs/react-native,janicduplessis/react-native,hammerandchisel/react-native,exponentjs/react-native,myntra/react-native,myntra/react-native,facebook/react-native