git-worktree.txt: fix typo "to"/"two", and add comma

Signed-off-by: Ben North <ben@redfrontdoor.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-worktree.txt

@@ -132,7 +132,7 @@ OPTIONS
 +
 If the last path components in the working tree's path is unique among
 working trees, it can be used to identify worktrees. For example if
-you only have to working trees at "/abc/def/ghi" and "/abc/def/ggg",
+you only have two working trees, at "/abc/def/ghi" and "/abc/def/ggg",
 then "ghi" or "def/ghi" is enough to point to the former working tree.
 
 DETAILS