Disable Focal on Harmonic (#2046)

Harmonic only supports Jammy so removing Focal CI.

Signed-off-by: Addisu Z. Taddese <[email protected]>

.github/workflows/ci.yml

@@ -3,23 +3,6 @@ name: Ubuntu CI
 on: [push, pull_request]
 
 jobs:
-  focal-ci:
-    runs-on: ubuntu-latest
-    name: Ubuntu Focal CI
-    steps:
-      - name: Checkout
-        uses: actions/checkout@v3
-      - uses: actions/setup-python@v3
-      - uses: pre-commit/[email protected]
-        with:
-          extra_args: --all-files
-      - name: Compile and test
-        id: ci
-        uses: gazebo-tooling/action-gz-ci@focal
-        with:
-          codecov-enabled: true
-          cppcheck-enabled: true
-          cpplint-enabled: true
   jammy-ci:
     runs-on: ubuntu-latest
     name: Ubuntu Jammy CI
@@ -36,3 +19,6 @@ jobs:
         with:
           # per bug https://github.com/gazebosim/gz-sim/issues/1409
           cmake-args: '-DBUILD_DOCS=OFF'
+          codecov-enabled: true
+          cppcheck-enabled: true
+          cpplint-enabled: true