🏗🐛 Silence autoprefixer deprecation warning by renaming browsers to overrideBrowserslist

[rsimha]

autoprefixer added a warning for a potentially breaking change in its new version by renaming the browsers field. See #22652 and postcss/autoprefixer#1226.

  Replace Autoprefixer browsers option to Browserslist config.
  Use browserslist key in package.json or .browserslistrc file.
  Using browsers option cause some error. Browserslist config 
  can be used for Babel, Autoprefixer, postcss-normalize and other tools.
  If you really need to use option, rename it to overrideBrowserslist.
  Learn more at:
  https://github.com/browserslist/browserslist#readme
  https://twitter.com/browserslist

This PR renames browsers to overrideBrowserslist as recommended in the warning.