Trivial Typo in hooks documentation

I don't have the source of git on my machine as I am just working from the 
debian packages, so I don't have a patch.  However there is a trivial type on 
the hooks.html documentation that I gues comes from the Documentation 
directory

The first sentence for both "update" and "post-update" hooks has an 
extra "is", marked in capitals below

"This hook is invoked by git-receive-pack on the remote repository, which IS 
happens when a git push is done on a local repository."



-- 
Alan Chandler
http://www.chandlerfamily.org.uk