ci: fix the platform image for gg-regressions to ubuntu-20.04 (github is migrating ubuntu-latest to 22.04)

Author: spytheman

.github/workflows/gg_regressions_ci.yml

@@ -10,7 +10,7 @@ on:
 
 jobs:
   gg-regressions:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     if: github.event_name != 'push' || github.event.ref == 'refs/heads/master' || github.event.repository.full_name != 'vlang/v'
     timeout-minutes: 10
     env: