Don't write platform specifically

This reverts commit bf8f09cf98913808d790133185b6d796d8db2cf3.

.woodpecker/docker.yaml

@@ -15,11 +15,13 @@ variables:
 
 steps:
   test-build:
-    image: docker:27-dind
-    commands:
-      - docker build -t source.hodakov.me/hdkv/phpbb:${CI_COMMIT_SHA:0:10} .
-    volumes:
-      - /var/run/docker.sock:/var/run/docker.sock
+    image: woodpeckerci/plugin-docker-buildx:5.1.0
+    privileged: true
+    settings:
+      dockerfile: Dockerfile
+      dry_run: true
+      repo: *repo
+      auto_tag: true
     when:
       event: pull_request
 
@@ -28,7 +30,6 @@ steps:
     privileged: true
     settings:
       dockerfile: Dockerfile
-      platforms: ${platform}
       repo: *repo
       registry: source.hodakov.me
       auto_tag: true