Minor fix to tests config

Author: bennothommo

.github/workflows/tests.yml

@@ -18,7 +18,8 @@ jobs:
         phpVersion: ['8.0', '8.1', '8.2', '8.3']
         winterBranch: ['develop']
         include:
-          - phpVersion: '7.4'
+          - operatingSystem: [ubuntu-latest]
+            phpVersion: '7.4'
             winterBranch: '1.1'
       fail-fast: false