OCD: Make the event_creator routes regex a code block

All the others are code blocks, so this one should be to (currently it is a blockquote).

Signed-off-by: Travis Ralston <travpc@gmail.com>

docs/workers.rst

@@ -230,7 +230,7 @@ file. For example::
 ``synapse.app.event_creator``
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-Handles non-state event creation. It can handle REST endpoints matching:
+Handles non-state event creation. It can handle REST endpoints matching::
 
     ^/_matrix/client/(api/v1|r0|unstable)/rooms/.*/send