GH Actions: update the CI workflow for the release of PHP 8.3 (#11726)

PHP 8.4 has been added as experimental.
And the "high" PHP builds for the variations have been updated to use PHP 8.3.

Co-authored-by: jrfnl <jrfnl@users.noreply.github.com>

.github/workflows/continuous-integration.yml

@@ -44,26 +44,26 @@ jobs:
             dependencies: lowest
             os: ubuntu-latest
             experimental: false
-          - php-version: "8.1"
+          - php-version: "8.3"
             dependencies: highest
             os: ubuntu-latest
             experimental: false
-          - php-version: "8.1"
+          - php-version: "8.3"
             os: windows-latest
             dependencies: locked
             experimental: false
-          - php-version: "8.1"
+          - php-version: "8.3"
             os: macos-latest
             dependencies: locked
             experimental: false
-          - php-version: "8.3"
+          - php-version: "8.4"
             dependencies: lowest-ignore
             os: ubuntu-latest
-            experimental: false
+            experimental: true
-          - php-version: "8.3"
+          - php-version: "8.4"
             dependencies: highest-ignore
             os: ubuntu-latest
-            experimental: false
+            experimental: true
 
     steps:
       - name: "Checkout"