minor #5054 [Changelog] fix changelog syntax (xabbuh)

This PR was merged into the master branch.

Discussion
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[Changelog] fix changelog syntax

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | 3.0+
| Fixed tickets |

Terminate the `tip` directive with a blank line.

Commits
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653ac94 fix changelog syntax

changelog.rst

@@ -12,6 +12,7 @@ documentation.
 
     Do you also want to participate in the Symfony Documentation? Take a look
     at the ":doc:`/contributing/documentation/overview`" article.
+
 February, 2015
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