Documentation/git-update-server-info.txt: Add -f alias for --force to documentation.

Signed-off-by: NNikolai Weibull <nikolai@bitwi.se>
Signed-off-by: NJunio C Hamano <junkio@cox.net>

Documentation/git-update-server-info.txt

@@ -22,7 +22,7 @@ pull decisions.  This command generates such auxiliary files.
 OPTIONS
 -------
 
---force::
+-f|--force::
 	Update the info files from scratch.