[skip ci] Remove empty param

In Docker meta step "prefix=" was empty

Author: edoardob90

.github/workflows/docker-build.yml

@@ -58,7 +58,7 @@ jobs:
             type=raw,value=${{ matrix.variant }}-${{ matrix.arch }},enable=${{ github.ref == 'refs/heads/main' }}
             type=raw,value=${{ matrix.variant }}-${{ matrix.arch }}-pr-${{ github.event.pull_request.number }},enable=${{ github.event_name == 'pull_request' }}
             type=raw,value=${{ matrix.variant }}-${{ matrix.arch }}-${{ github.ref_name }},enable=${{ startsWith(github.ref, 'refs/tags/') }}
-            type=raw,value=${{ matrix.variant }}-${{ matrix.arch }}-sha-${{ github.sha }},prefix=
+            type=raw,value=${{ matrix.variant }}-${{ matrix.arch }}-sha-${{ github.sha }}
 
       - name: Build and push
         uses: docker/build-push-action@v6