Update HOWTO-RELEASE.md regarding auto_tag_stable.yml

Update the procedure to update the workflow that automatically refreshes
the "stable" tag from commits in the current release branch.

HOWTO-RELEASE.md

@@ -87,17 +87,37 @@ If the database references data from an updated PROJ-data package, update
 
 *Skip this step if you are preparing a patch release or RC2 and later.*
 
-Create the branch:
+a) Remove the .github/workflows/auto_tag_stable.yml from the now old maintenance
+   branch. That is if releasing 9.6, remove it from 9.5
 
-```sh
-git branch x.y
-```
+   ```sh
+   git checkout 9.5
+   cp .github/workflows/auto_tag_stable.yml /tmp
+   git rm .github/workflows/auto_tag_stable.yml -m "Remove obsolete auto_tag_stable.yml workflow"
+   git push origih 9.5
+   ```
+
+b) Create the new branch:
+
+  ```sh
+  git checkout master
+  git branch x.y
+  ```
+
+  where `x` is the major version number and `y` is the minor version number. Bug
+  fixes found in the release candidates should be pushed to master and
+  subsequently cherry-picked to the maintenance branch.
+
+c) Create auto_tag_stable.yml workflow in the new branch
 
-where `x` is the major version number and `y` is the minor version number. Bug
-fixes found in the release candidates should be pushed to master and
-subsequently cherry-picked to the maintenance branch.
+  ```sh
+   cp /tmp/auto_tag_stable.yml .github/workflows/auto_tag_stable.yml
+   sed -i "s/9.5/9.6/" .github/workflows/auto_tag_stable.yml  # Update the branch
+   git add .github/workflows/auto_tag_stable.yml
+   git commit .github/workflows/auto_tag_stable.yml -m "Add auto_tag_stable.yml"
+  ```
 
-*Push branch upstream.*
+d) *Push branch upstream.*
 
 ### 1.7 Prepare and upload archives