ci: Drop support for ARM v7 platform (#2943)

This platform has had a deprecation notice for 6 months. It is not worth continuing to maintain support for.

.github/workflows/generic_build.yml

@@ -76,13 +76,12 @@ jobs:
       - name: 'Set up QEMU'
         uses: docker/setup-qemu-action@v2.1.0
         with:
-          platforms: arm64,arm
+          platforms: arm64
 
       - name: 'Set up Docker Buildx'
         uses: docker/setup-buildx-action@v2.2.1
 
-      # NOTE: AMD64 can build within 2 minutes, ARM adds 13 minutes. 330MB each
-      # ARMv7 can build in parallel, adding no extra time (but does add 150MB cache size).
+      # NOTE: AMD64 can build within 2 minutes
       - name: 'Build images'
         uses: docker/build-push-action@v3.2.0
         with:

.github/workflows/generic_publish.yml

@@ -37,7 +37,7 @@ jobs:
       - name: 'Set up QEMU'
         uses: docker/setup-qemu-action@v2.1.0
         with:
-          platforms: arm64,arm
+          platforms: arm64
 
       - name: 'Set up Docker Buildx'
         uses: docker/setup-buildx-action@v2.2.1
@@ -78,7 +78,7 @@ jobs:
           build-args: |
             VCS_REVISION=${{ github.sha }}
             VCS_VERSION=${{ steps.get-version.outputs.version }}
-          platforms: linux/amd64,linux/arm/v7,linux/arm64
+          platforms: linux/amd64,linux/arm64
           push: true
           tags: ${{ steps.prep.outputs.tags }}
           cache-from: type=local,src=/tmp/.buildx-cache

.github/workflows/scheduled_builds.yml

@@ -13,7 +13,7 @@ jobs:
     name: 'Build Images'
     uses: docker-mailserver/docker-mailserver/.github/workflows/generic_build.yml@master
     with:
-      platforms: linux/amd64,linux/arm/v7,linux/arm64
+      platforms: linux/amd64,linux/arm64
 
   publish-images:
     name: 'Publish Images'

.github/workflows/test_merge_requests.yml

@@ -30,8 +30,8 @@ jobs:
     name: 'Build ARM64 Image'
     # Dependency ensures the cache-key is only created for AMD64 builds.
     # ARM64 will not be able to use this cache, building from scratch each time.
-    # Expect about 13 minutes build time until adopting `type=gha` with scopes for cache.
+    # Expect about 2 minutes extra build time until adopting `type=gha` with scopes for cache.
     needs: build-image-amd64
     uses: docker-mailserver/docker-mailserver/.github/workflows/generic_build.yml@master
     with:
-      platforms: linux/arm/v7,linux/arm64
+      platforms: linux/arm64