docs: do not document the git remote-testgit command

Since 7ded055 (build: do not install git-remote-testgit, 2013-06-07),
we do not install it. Therefore it makes no sense to document it,
either.

Signed-off-by: Johannes Schindelin <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: dscho

Documentation/git-remote-testgit.txt

@@ -513,8 +513,6 @@ linkgit:git-remote-ext[1]
 
 linkgit:git-remote-fd[1]
 
-linkgit:git-remote-testgit[1]
-
 linkgit:git-fast-import[1]
 
 GIT