TO-DROP: only verify cbl-mariner

... until I get it right...

Signed-off-by: Johannes Schindelin <[email protected]>

.github/workflows/validate-install-from-source.yml

@@ -3,8 +3,6 @@ name: validate-install-from-source
 on:
   workflow_dispatch:
   push:
-    branches:
-      - main
 
 jobs:
   docker:
@@ -14,20 +12,6 @@ jobs:
       fail-fast: false
       matrix:
         vector:
-        - image: ubuntu
-        - image: debian:bullseye
-        - image: fedora
-        # Centos no longer officially maintains images on Docker Hub. However,
-        # tgagor is a contributor who pushes updated images weekly, which should
-        # be sufficient for our validation needs.
-        - image: tgagor/centos
-        - image: redhat/ubi8
-        - image: alpine
-        - image: alpine:3.14.10
-        - image: opensuse/leap
-        - image: opensuse/tumbleweed
-        - image: registry.suse.com/suse/sle15:15.4.27.11.31
-        - image: archlinux
         - image: mcr.microsoft.com/cbl-mariner/base/core:2.0
     container: ${{matrix.vector.image}}
     steps: