Don't build for ARM v7 as that currently still fails

.github/workflows/build.yml

@@ -43,7 +43,7 @@ jobs:
               uses: docker/build-push-action@v2
               with:
                 context: .
-                platforms: linux/amd64,linux/arm64,linux/arm/v7
+                platforms: linux/amd64,linux/arm64
                 push: true
                 build-args: |
                   MUMBLE_VERSION=${{ env.MUMBLE_VERSION }}