minor #4480 Fix spelling (nurikabe)

This PR was submitted for the master branch but it was merged into the 2.3 branch instead (closes #4480).

Discussion
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Fix spelling

Commits
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bd99a31 Fix spelling

Author: wouterj

book/routing.rst

@@ -1132,7 +1132,7 @@ see :ref:`route-parameters-controller-arguments`.
 .. tip::
 
     The special ``$_route`` variable is set to the name of the route that was
-    matced.
+    matched.
 
 You can even add extra information to your route definition and access it
 within your controller. For more information on this topic,