Use free CI runner for lint (#11)

Author: LegNeato

.github/workflows/ci.yaml

@@ -112,7 +112,7 @@ jobs:
 
   lint:
     name: Lint
-    runs-on: ubuntu-20.04-16core
+    runs-on: ubuntu-20.04
     steps:
       # Note that we are explicitly NOT checking out submodules, to validate
       # that we haven't accidentally enabled spirv-tools native compilation