emacs: Change group link.

We changed the group from g/repo-gerrit to g/chromacs.

BUG=None
TEST=Used the link.

Change-Id: I290618cdd54897285b06ade5c1854a7da567e034
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/dev-util/+/2337173
Tested-by: Aaron Massey <aaronmassey@chromium.org>
Reviewed-by: Sean McAllister <smcallis@google.com>
Reviewed-by: Jack Rosenthal <jrosenth@chromium.org>
Commit-Queue: Aaron Massey <aaronmassey@chromium.org>
diff --git a/contrib/emacs/README.md b/contrib/emacs/README.md
index 0708aa2..ef0b41d 100644
--- a/contrib/emacs/README.md
+++ b/contrib/emacs/README.md
@@ -80,4 +80,4 @@
 
 Any questions or feedback is greatly appreciated!
 
-[Chromacs Group](https://groups.google.com/a/google.com/g/repo-gerrit)
+[Chromacs Group](https://groups.google.com/a/google.com/g/chromacs)