Update docker-publish.yml (#1)

Use cosign 1.6.0

Author: tcrouch

.github/workflows/docker-publish.yml

@@ -37,16 +37,11 @@ jobs:
 
       # Install the cosign tool except on PR
       # https://github.com/sigstore/cosign-installer
-      - name: Install go
-        if: github.event_name != 'pull_request'
-        uses: actions/setup-go@v2
-        with:
-          go-version: '1.17.x'
       - name: Install cosign
         if: github.event_name != 'pull_request'
         uses: sigstore/cosign-installer@main
         with:
-          cosign-release: 'main'
+          cosign-release: 'v1.6.0'
 
       - name: Set up QEMU
         uses: docker/setup-qemu-action@v1