build(deps): bump docker/build-push-action from 3 to 6 (#398)

Bumps [docker/build-push-action](https://github.com/docker/build-push-action) from 3 to 6.
- [Release notes](https://github.com/docker/build-push-action/releases)
- [Commits](docker/build-push-action@v3...v6)

---
updated-dependencies:
- dependency-name: docker/build-push-action
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

.github/workflows/build.yml

@@ -104,7 +104,7 @@ jobs:
 
     # First build the base image locally (needed for subsequent builds)
     - name: Build Docker image (base)
-      uses: docker/build-push-action@v3
+      uses: docker/build-push-action@v6
       with:
         tags: gptme:latest
         file: ./scripts/Dockerfile
@@ -113,7 +113,7 @@ jobs:
 
     # Push base image to registry if on master/tag
     - name: Push Docker image (base)
-      uses: docker/build-push-action@v3
+      uses: docker/build-push-action@v6
       if: env.SHOULD_PUSH == 'true'
       with:
         tags: |
@@ -125,7 +125,7 @@ jobs:
 
     # Build and push eval image
     - name: Build and push Docker image (eval)
-      uses: docker/build-push-action@v3
+      uses: docker/build-push-action@v6
       with:
         tags: |
           ghcr.io/${{ env.OWNER_LC }}/gptme-eval:latest
@@ -137,7 +137,7 @@ jobs:
     # Now the full eval image
     # NOTE: takes a long time and leads to a big (1GB+) image
     #- name: Build and push Docker image (eval-full)
-    #  uses: docker/build-push-action@v3
+    #  uses: docker/build-push-action@v6
     #  with:
     #    tags: |
     #      ghcr.io/${{ env.OWNER_LC }}/gptme-eval-full:latest