rebase docs: fix "gitlink" typo

Change it to "linkgit" so that the reference is properly rendered.

Signed-off-by: Kyle Meyer <kyle@kyleam.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-rebase.txt

@@ -391,7 +391,7 @@ have the long commit hash prepended to the format.
 +
 By default, or when `no-rebase-cousins` was specified, commits which do not
 have `<upstream>` as direct ancestor will keep their original branch point,
-i.e. commits that would be excluded by gitlink:git-log[1]'s
+i.e. commits that would be excluded by linkgit:git-log[1]'s
 `--ancestry-path` option will keep their original ancestry by default. If
 the `rebase-cousins` mode is turned on, such commits are instead rebased
 onto `<upstream>` (or `<onto>`, if specified).