chore: add php 8.5 to testing matrix (#8816)

Author: bshaffer

.github/workflows/unit-tests.yaml

@@ -12,7 +12,7 @@ jobs:
     strategy:
       matrix:
         platform: [ubuntu-latest, windows-latest]
-        php: [ "8.1", "8.2", "8.3", "8.4" ]
+        php: [ "8.1", "8.2", "8.3", "8.4", "8.5" ]
         extensions: ["grpc-1.54.0"]
         type: ["Unit Test"]
         include: