minor symfony#10414 [Encore] Updates links to babel-preset-env and browserslist (royklutman)

This PR was merged into the 3.4 branch.

Discussion
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[Encore] Updates links to babel-preset-env and browserslist

Commits
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d96bae1 Updated links

Author: javiereguiluz

frontend/encore/postcss.rst

@@ -75,6 +75,6 @@ See `browserslist`_ for more details on the syntax.
 .. _`PostCSS`: http://postcss.org/
 .. _`autoprefixing`: https://github.com/postcss/autoprefixer
 .. _`linting`: https://stylelint.io/
-.. _`browserslist`: https://github.com/ai/browserslist
-.. _`babel-preset-env`: https://github.com/babel/babel-preset-env
+.. _`browserslist`: https://github.com/browserslist/browserslist
+.. _`babel-preset-env`: https://github.com/babel/babel/tree/master/packages/babel-preset-env
 .. _`postcss-loader`: https://github.com/postcss/postcss-loader