Quote '4.80' so its not interpreted as 4.8

Author: fredemmott

.github/workflows/build-and-test.yml

@@ -13,7 +13,7 @@ jobs:
       matrix:
         os: [ ubuntu , macos ]
         hhvm:
-          - 4.80
+          - "4.80"
           - latest
           - nightly
     runs-on: ${{matrix.os}}-latest