gitk: discourage AI contributions

Since the provenance of code generated by AI cannot be tracked with
confidence, which would be necessary to sign off a contribution, tell
contributors not to use AI.

Signed-off-by: Johannes Sixt <j6t@kdbg.org>

README.md

@@ -79,13 +79,14 @@ are also accepted.
 All commits must be signed off (use `git commit --signoff`) and should
 have commit messages prefixed with `gitk:`.
 
-Email Patches
--------------
-
 Send patches to git@vger.kernel.org and CC j6t@kdbg.org. See the Git
 project's [patch submission guidelines](https://git-scm.com/docs/SubmittingPatches)
 for detailed instructions on creating and sending patches.
 
+Please do not submit work that originated from AI, because this project
+is down-streamed to the Git project, which has a rather
+[strict AI guideline](https://git-scm.com/docs/SubmittingPatches#ai).
+
 License
 =======