ci: Change names for release branches from rel-MAJOR.MINOR to vMAJOR

This naming scheme gives us the best support for readthedocs.

References #2814

.github/workflows/ci.yaml

@@ -4,13 +4,14 @@ on:
   push:
     branches:
       - main
-      - rel-*
+      - v[0-9]+
     tags:
       - v*
   pull_request:
     branches:
       - main
-      - rel-*
+      - v[0-9]+
+
 concurrency:
   group: ${{ github.workflow }}-${{ github.ref }}
   # Terminate all previous runs of the same workflow for pull requests

.github/workflows/docs.yaml

@@ -4,11 +4,11 @@ on:
   push:
     branches:
     - main
-    - rel-*
+    - v[0-9]+
   pull_request:
     branches:
     - main
-    - rel-*
+    - v[0-9]+
 
 jobs:
   build: