CI: Drop Golang from Coverity run

Something has changed recently in Github Actions and golang is no longer
available from the internal mirror:

  https://github.com/xen-project/xen/actions/runs/11539340171/job/32120834909

I can't find

.github/workflows/coverity.yml

@@ -12,6 +12,7 @@ jobs:
     steps:
     - name: Install build dependencies
       run: |
+        sudo apt-get update
         sudo apt-get install -y \
           build-essential \
           git-core \