minor #10240 Small fix to syntax (Fixes Travis) (aequasi)

This PR was submitted for the master branch but it was merged into the 4.1 branch instead (closes #10240).

Discussion
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Small fix to syntax (Fixes Travis)

Fixes Travis

Commits
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72e6dcd Small fix to syntax

Author: xabbuh

components/var_dumper.rst

@@ -119,7 +119,7 @@ Inside a Symfony application, the output of the dump server is configured with
 the :ref:`dump_destination option <configuration-debug-dump_destination>` of the
 ``debug`` package.
 
-Outside a Symfony application, use the ``ServerDumper`` class:
+Outside a Symfony application, use the ``ServerDumper`` class::
 
     require __DIR__.'/vendor/autoload.php';