minor #13966 [FrameworkBundle] Remove asset from require-dev (dunglas)

This PR was merged into the 2.7 branch.

Discussion
----------

[FrameworkBundle] Remove asset from require-dev

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | n/a
| License       | MIT
| Doc PR        | n/a

Not needed because already in `require`.

Commits
-------

3a29bb6 [FrameworkBundle] Remove asset from require-dev

Author: fabpot

src/Symfony/Bundle/FrameworkBundle/composer.json

@@ -34,7 +34,6 @@
     },
     "require-dev": {
         "symfony/phpunit-bridge": "~2.7|~3.0.0",
-        "symfony/asset": "~2.7|~3.0.0",
         "symfony/browser-kit": "~2.4|~3.0.0",
         "symfony/console": "~2.6|~3.0.0",
         "symfony/css-selector": "~2.0,>=2.0.5|~3.0.0",