minor #9185 mention phpunit bridge in bundle best practices (dbu, javiereguiluz)

This PR was merged into the 4.0 branch.

Discussion
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mention phpunit bridge in bundle best practices

i noticed that the bundle best practices don't mention the phpunit bridge. should we go even further and add it to the list of things a bundle should be using?

Commits
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4854c03 Reword
dce07d5 mention phpunit bridge in bundle best practices

Author: javiereguiluz

bundles/best_practices.rst

@@ -235,6 +235,8 @@ of Symfony and the latest beta release:
 
     script:
         - composer validate --strict --no-check-lock
+        # simple-phpunit is the PHPUnit wrapper provided by the PHPUnit Bridge component and
+        # it helps with testing legacy code and deprecations (composer require symfony/phpunit-bridge)
         - ./vendor/bin/simple-phpunit $PHPUNIT_FLAGS
 
 Consider using `Travis cron`_ too to make sure your project is built even if