Drop the CI builds that require Ubuntu 18.04, which has been EoL for …

…several months

The nodejs v20 actions require at least Ubuntu 20.04 to run. Downgrading
to nodejs 16 and extending its agony for a few more months until they
become fully unsupported seems pointless to me.

Signed-off-by: Haru <haru@dotalux.com>

.github/workflows/controller.yml

@@ -35,10 +35,6 @@ jobs:
     needs: build
     if: ${{ !failure() && !cancelled() }}
     uses: ./.github/workflows/gccold2.yml
-  gccold3:
-    needs: build
-    if: ${{ !failure() && !cancelled() }}
-    uses: ./.github/workflows/gccold3.yml
   gccsnapshot_test:
     needs: build
     if: ${{ !failure() && !cancelled() }}