remove docker_builder step (#64654)

.cirrus.yml

@@ -465,23 +465,3 @@ task:
       script:
         - ulimit -S -n 2048 # https://github.com/flutter/flutter/issues/2976
         - dart --enable-asserts ./dev/bots/codesign.dart
-
-docker_builder:
-  # Only build a new docker image when we tag a release (for dev, beta, or
-  # stable). Note: tagging a commit and pushing to a release branch are
-  # different cirrus triggers. See a tag CI run at e.g.
-  # https://cirrus-ci.com/github/flutter/flutter/v1.2.3
-  name: docker_build
-  only_if: $CIRRUS_TAG != ''
-  environment:
-    GCLOUD_CREDENTIALS: ENCRYPTED[f7c098d4dd7f5ee1bfee0bb7e944cce72efbe10e97ad6440ae72de4de6a1c24d23f421a2619c668e94377fb64b0bb3e6]
-  # Do not add more tasks here. The behavior of failing dependencies is non-ideal for infra health.
-  # See also: https://github.com/flutter/flutter/pull/49454
-  depends_on:
-    - docs-linux
-    - analyze-linux
-  build_script:
-    - cd "$CIRRUS_WORKING_DIR/dev/ci/docker_linux"
-    - ./docker_build.sh
-    - ./docker_login.sh
-    - ./docker_push.sh