Change CI: 5.1rc1 -> 5.1

Author: bckohan

.github/workflows/test.yml

@@ -12,7 +12,7 @@ jobs:
           - '3.2' # LTS April 2024
           - '4.2' # LTS April 2026
           - '5.0' # April 2025
-          - '5.1rc1' # December 2025
+          - '5.1' # December 2025
         exclude:
           - python-version: '3.7'
             django-version: '5.0'
@@ -27,11 +27,11 @@ jobs:
           - python-version: '3.12'
             django-version: '3.2'
           - python-version: '3.7'
-            django-version: '5.1rc1'
+            django-version: '5.1'
           - python-version: '3.8'
-            django-version: '5.1rc1'
+            django-version: '5.1'
           - python-version: '3.9'
-            django-version: '5.1rc1'
+            django-version: '5.1'
 
     steps:
     - uses: actions/checkout@v4