In error I edited the 'post-revprop-change' file instead of the 'pre-revprop-change' in the hooks directory.
The edit I made was to copy in the instructions described here which allow changes to be made to the log entry. Obviously this doesn't make sense for the 'post-revprop-change' hook so I would like to undo the change. A simple thing would be just to delete the executable, but as I overwrote the template, I would like to know what the know what instructions should exist in this file. Apologies if my question seems convoluted.
The template is created anytime you create a new repository. So just create a new repository, copy the template, and delete the new one.
The template doesn't actually do anything, so you lose no functionality if you just delete the file. The same information in the template is documented in the Subversion manual