chore(deps): bump docker/login-action in /.github/actions/docker-merge (#741)

Bumps [docker/login-action](https://github.com/docker/login-action) from 3 to 4.
- [Release notes](https://github.com/docker/login-action/releases)
- [Commits](docker/login-action@v3...v4)

---
updated-dependencies:
- dependency-name: docker/login-action
  dependency-version: '4'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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Author: dependabot[bot]

.github/actions/docker-merge/action.yml

@@ -46,14 +46,14 @@ runs:
 
     - name: Login to Docker Hub
       if: ${{ inputs.docker-password }}
-      uses: docker/login-action@v3
+      uses: docker/login-action@v4
       with:
         username: ${{ inputs.docker-username }}
         password: ${{ inputs.docker-password }}
 
     - name: Log in to GHCR
       if: ${{ inputs.ghcr-password }}
-      uses: docker/login-action@v3
+      uses: docker/login-action@v4
       with:
         registry: ghcr.io
         username: ${{ inputs.ghcr-username }}