minor #11934 Add https for symfony url (Amin-Hosseini)

This PR was submitted for the master branch but it was merged into the 3.4 branch instead (closes #11934).

Discussion
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Add https for symfony url

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Commits
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676454f Add https for symfony url

Author: javiereguiluz

frontend.rst

@@ -117,6 +117,6 @@ Other Front-End Articles
 .. _`Webpack`: https://webpack.js.org/
 .. _`Webpacker`: https://github.com/rails/webpacker
 .. _`Mix`: https://laravel.com/docs/mix
-.. _`Symfony`: http://symfony.com/
+.. _`Symfony`: https://symfony.com/
 .. _`Full API`: https://github.com/symfony/webpack-encore/blob/master/index.js
 .. _`Webpack Encore screencast series`: https://symfonycasts.com/screencast/webpack-encore