revert: diff-hl

dgutov/diff-hl@39f076efa8 -> dgutov/diff-hl@0fe1bc0fd8

diff-hl introduced changes that require Emacs 31+ that can't be
trivially advised out or worked around. Until it's resolved upstream,
I've reverted diff-hl to one commit behind dgutov/diff-hl@7a89c85b89.

Fix: #8464
Ref: dgutov/diff-hl@7a89c85b89
Amend: a1121acc94

modules/ui/vc-gutter/config.el

@@ -171,7 +171,10 @@ Respects `diff-hl-disable-on-remote'."
                 (null (buffer-file-name (buffer-base-buffer)))
                 (null (get-buffer-window (current-buffer))))
       (setq diff-hl-timer nil)
-      (if (diff-hl--use-async-p)
+      (if (and diff-hl-update-async
+               (not
+                (run-hook-with-args-until-success 'diff-hl-async-inhibit-functions
+                                                  default-directory)))
           (progn
             (+vc-gutter--kill-thread)
             (setq +vc-gutter--diff-hl-thread