minor #15701 [SecurityBundle] allow more versions of the ACL package (xabbuh)

This PR was merged into the 2.8 branch.

Discussion
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[SecurityBundle] allow more versions of the ACL package

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

This actually is the version that is required when using the Symfony SE
(`symfony/symfony` requires `symfony/security-acl` in version `~2.7`).

Commits
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3a15921 allow more versions of the ACL package

Author: fabpot

composer.json

@@ -18,7 +18,7 @@
     "require": {
         "php": ">=5.3.9",
         "symfony/security": "~2.8|~3.0.0",
-        "symfony/security-acl": "~2.8|~3.0.0",
+        "symfony/security-acl": "~2.7|~3.0.0",
         "symfony/http-kernel": "~2.2|~3.0.0"
     },
     "require-dev": {