upgrade nim version to 1.4.8 in `test.yml`

.github/workflows/test.yml

@@ -25,7 +25,7 @@ jobs:
           #- windows-latest
           #- macOS-latest
         nim_version:
-          - '1.2.0'
+          - '1.4.8'
           - 'stable'
     needs: before
     env: