minor #12398 [TwigBridge] TwigExtractor tests require the Finder component (xabbuh)

This PR was merged into the 2.3 branch.

Discussion
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[TwigBridge] TwigExtractor tests require the Finder component

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

The tests for the `TwigExtractor`(as introduced in #12377) require the Finder component to be run properly.

Commits
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8fc3e03 TwigExtractor tests require the Finder component

src/Symfony/Bridge/Twig/composer.json

@@ -20,6 +20,7 @@
         "twig/twig": "~1.12"
     },
     "require-dev": {
+        "symfony/finder": "~2.3",
         "symfony/form": "~2.2",
         "symfony/http-kernel": "~2.2",
         "symfony/routing": "~2.2",
@@ -29,6 +30,7 @@
         "symfony/security": "~2.0"
     },
     "suggest": {
+        "symfony/finder": "",
         "symfony/form": "",
         "symfony/http-kernel": "",
         "symfony/routing": "",