ci: limit redis service setup to 5.0.x PR workflow

.github/workflows/pull_request_5x.yml

@@ -8,6 +8,16 @@ jobs:
   build:
 
     runs-on: ubuntu-latest
+    services:
+      redis:
+        image: redis:7-alpine
+        ports:
+          - 6379:6379
+        options: >-
+          --health-cmd "redis-cli ping"
+          --health-interval 10s
+          --health-timeout 5s
+          --health-retries 5
 
     steps:
     - uses: actions/checkout@v1