git-svn.txt: reword description of gc command

It's redundant to say that $GIT_DIR/svn/<refname>/unhandled.log or
$GIT_DIR/svn/<refname>/index is in .git/svn when $GIT_DIR is '.git', and
is wrong when $GIT_DIR is not '.git'

Also, a '/' was missing from the pathname $GIT_DIR/svn/<refname>/index .

Signed-off-by: Keshav Kini <keshav.kini@gmail.com>
Signed-off-by: Eric Wong <normalperson@yhbt.net>

Documentation/git-svn.txt

@@ -435,8 +435,8 @@ Any other arguments are passed directly to 'git log'
 	specific revision.
 
 'gc'::
-	Compress $GIT_DIR/svn/<refname>/unhandled.log files in .git/svn
-	and remove $GIT_DIR/svn/<refname>index files in .git/svn.
+	Compress $GIT_DIR/svn/<refname>/unhandled.log files and remove
+	$GIT_DIR/svn/<refname>/index files.
 
 'reset'::
 	Undoes the effects of 'fetch' back to the specified revision.