git-repack.txt: remove spurious ")"

Drop the ")" at the end of this paragraph. There's a parenthetical
remark in this paragraph, but it's been closed on the line above.

Signed-off-by: Martin Ågren <martin.agren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-repack.txt

@@ -186,7 +186,7 @@ When `--unpacked` is specified, loose objects are implicitly included in
 this "roll-up", without respect to their reachability. This is subject
 to change in the future. This option (implying a drastically different
 repack mode) is not guaranteed to work with all other combinations of
-option to `git repack`).
+option to `git repack`.
 
 CONFIGURATION
 -------------