resources: Updated URL to `stable` instead of `master`

Change-Id: Ie9e29bdf991d1b8efef73e053f760f9adedc63d7
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5-resources/+/35458
Reviewed-by: Bobby R. Bruce <bbruce@ucdavis.edu>
Maintainer: Bobby R. Bruce <bbruce@ucdavis.edu>
Tested-by: Bobby R. Bruce <bbruce@ucdavis.edu>
diff --git a/README.md b/README.md
index 9648b9f..909dcda 100755
--- a/README.md
+++ b/README.md
@@ -29,7 +29,7 @@
 found with `git tag`. The develop branch contains code under development and
 will be merged into the master branch, then tagged, as part of the next release
 of gem5. More information on gem5 release procedures can be found [here](
-https://gem5.googlesource.com/public/gem5/+/refs/heads/master/CONTRIBUTING.md#releases).
+https://gem5.googlesource.com/public/gem5/+/refs/heads/stable/CONTRIBUTING.md#releases).
 Any release procedures related to the gem5 source can be assumed to be
 applicable to gem5-resources.