Removed bower asset exclusion

This is recommended by the Symfony docs:

http://symfony.com/doc/current/frontend/bower.html#should-i-git-ignore-or-commit-bower-assets

Author: robinkanters

Symfony.gitignore

@@ -31,9 +31,6 @@
 /web/bundles/
 /web/uploads/
 
-# Assets managed by Bower
-/web/assets/vendor/
-
 # PHPUnit
 /app/phpunit.xml
 /phpunit.xml