[#2977] Improve wording of best practice regarding name clashes.

The documentation previously talked about sharing databases which could
be misunderstood as the possibility of sharing PostgreSQL databases
between CKAN instances (instead of sharing Redis databases, which was
the intended meaning).

doc/extensions/best-practices.rst

@@ -80,10 +80,10 @@ the name of your extension. For example:
   begin with the name of your extension. For example
   ``my_extension:super-special-job-queue``.
 
-In some situations, resources like databases may even be shared between
-multiple CKAN *instances*, which requires an even higher degree of uniqueness
-for the corresponding names. In that case, you should also prefix your
-identifiers with the CKAN site ID, which is available via
+In some situations, a resource may even be shared between multiple CKAN
+*instances*, which requires an even higher degree of uniqueness for the
+corresponding names. In that case, you should also prefix your identifiers with
+the CKAN site ID, which is available via
 
 ::