minor #9158 Add example for Finder::exclude (theofidry, javiereguiluz)

This PR was merged into the 2.7 branch.

Discussion
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Add example for Finder::exclude

Follow up of symfony/symfony#25945

Commits
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99b0f7a Reworded the note as a code comment
5e96849 Update finder.rst
9970d42 Add example for Finder::exclude

Author: javiereguiluz

components/finder.rst

@@ -103,6 +103,7 @@ Each pattern has to resolve to at least one directory path.
 Exclude directories from matching with the
 :method:`Symfony\\Component\\Finder\\Finder::exclude` method::
 
+    // directories passed as argument must be relative to the ones defined with the in() method
     $finder->in(__DIR__)->exclude('ruby');
 
 .. versionadded:: 2.3