minor symfony#11521 add blank line before directive (OskarStark)

This PR was merged into the 3.4 branch.

Discussion
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add blank line before directive

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Commits
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4ef5b97 add blank line before directive

Author: javiereguiluz

forms.rst

@@ -707,6 +707,7 @@ There's a lot more to learn and a lot of *powerful* tricks in the form system.
 
 Learn more
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+
 .. toctree::
     :maxdepth: 1
     :glob: