pull: remove --update-head-ok from documentation

'git pull' implicitly passes --update-head-ok to 'git fetch', but
doesn't itself accept that option from users.  That makes sense, as it
wouldn't work without the possibility to update HEAD.  Remove the option
from the command's documentation to match its actual behavior.

Signed-off-by: René Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/fetch-options.txt

@@ -204,7 +204,6 @@ ifndef::git-pull[]
 	recursion (such as settings in linkgit:gitmodules[5] and
 	linkgit:git-config[1]) override this option, as does
 	specifying --[no-]recurse-submodules directly.
-endif::git-pull[]
 
 -u::
 --update-head-ok::
@@ -214,6 +213,7 @@ endif::git-pull[]
 	to communicate with 'git fetch', and unless you are
 	implementing your own Porcelain you are not supposed to
 	use it.
+endif::git-pull[]
 
 --upload-pack <upload-pack>::
 	When given, and the repository to fetch from is handled