git-commit.txt: list post-rewrite in HOOKS section

The hook was added in a86ed83cce (Merge branch 'tr/notes-display' -
2010-03-24), which updated githooks.txt but not git-commit.txt.

git-commit.txt was later updated in e858af6d50 (commit: document a
couple of options - 2012-06-08). Since this commit focused on command
line options, this section was probably forgotten.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-commit.txt

@@ -460,7 +460,7 @@ order).  See linkgit:git-var[1] for details.
 HOOKS
 -----
 This command can run `commit-msg`, `prepare-commit-msg`, `pre-commit`,
-and `post-commit` hooks.  See linkgit:githooks[5] for more
+`post-commit` and `post-rewrite` hooks.  See linkgit:githooks[5] for more
 information.
 
 FILES