Add testing of moodle-plugin-ci on PHP 8.4

Author: marinaglancy

.github/workflows/test.yml

@@ -75,7 +75,7 @@ jobs:
       fail-fast: false
       matrix:
         include:
-          - php: '8.3'
+          - php: '8.4'
             moodle-branch: 'main'
             moodle-app: 'true'
           - php: '8.3'
@@ -202,7 +202,7 @@ jobs:
       matrix:
         include:
           # Each supported PHP version once. That's enough.
-          - php: '8.3'
+          - php: '8.4'
             moodle-branch: 'main'
             moodle-app: 'true'
           - php: '8.3'
@@ -294,6 +294,7 @@ jobs:
       matrix:
         include:
           # Each supported PHP version once. That's enough.
+          - php: '8.4'
           - php: '8.3'
           - php: '8.2'
           - php: '8.1'