Remove unused eslint comment (facebook#6674)

Author: mohitsinghs

packages/react-dev-utils/formatWebpackMessages.js

@@ -15,7 +15,6 @@ function isLikelyASyntaxError(message) {
 }
 
 // Cleans up webpack error messages.
-// eslint-disable-next-line no-unused-vars
 function formatMessage(message) {
  let lines = message.split('\n');