convert: correct 'hooks' section name in online help

The section name for hooks is not 'hook', but 'hooks'.

hgext/convert/__init__.py

@@ -191,12 +191,12 b' def convert(ui, src, dest=None, revmapfi'
         branch indicated in the regex as the second parent of the
         changeset. Default is ``{{mergefrombranch ([-\\w]+)}}``
 
-    :hook.cvslog: Specify a Python function to be called at the end of
+    :hooks.cvslog: Specify a Python function to be called at the end of
         gathering the CVS log. The function is passed a list with the
         log entries, and can modify the entries in-place, or add or
         delete them.
 
-    :hook.cvschangesets: Specify a Python function to be called after
+    :hooks.cvschangesets: Specify a Python function to be called after
         the changesets are calculated from the CVS log. The
         function is passed a list with the changeset entries, and can
         modify the changesets in-place, or add or delete them.

tests/test-convert.t

@@ -172,11 +172,11 b''
                     will add the most recent revision on the branch indicated in
                     the regex as the second parent of the changeset. Default is
                     "{{mergefrombranch ([-\w]+)}}"
-      hook.cvslog   Specify a Python function to be called at the end of
+      hooks.cvslog  Specify a Python function to be called at the end of
                     gathering the CVS log. The function is passed a list with
                     the log entries, and can modify the entries in-place, or add
                     or delete them.
-      hook.cvschangesets
+      hooks.cvschangesets
                     Specify a Python function to be called after the changesets
                     are calculated from the CVS log. The function is passed a
                     list with the changeset entries, and can modify the