Update runners to ubuntu-24.04 from deprecated ubuntu-20.04 label

Author: billnapier

.github/workflows/ci.yml

@@ -116,7 +116,7 @@ jobs:
     - run: bazel build :all
     - run: bazel test :chromobius_test
   build_clang:
-    runs-on: ubuntu-20.04
+    runs-on: 'ubuntu-24.04'
     steps:
     - uses: actions/checkout@v3
     - run: |