fix: remove Docker Hub login from CI builds

Harbor dockerhub-cache proxy handles Docker Hub pulls without
needing direct Docker Hub authentication. Removes the failing
index.docker.io login blocks from all build pipeline steps.

.woodpecker/build-2.yml

@@ -24,11 +24,6 @@ steps:
           from_secret: harbor_username
         password:
           from_secret: harbor_password
-      - registry: https://index.docker.io/v1/
-        username:
-          from_secret: docker_username
-        password:
-          from_secret: docker_password
       tags:
       - ${CI_COMMIT_SHA}
       - latest
@@ -65,11 +60,6 @@ steps:
           from_secret: harbor_username
         password:
           from_secret: harbor_password
-      - registry: https://index.docker.io/v1/
-        username:
-          from_secret: docker_username
-        password:
-          from_secret: docker_password
       tags:
       - ${CI_COMMIT_SHA}
       - latest
@@ -106,11 +96,6 @@ steps:
           from_secret: harbor_username
         password:
           from_secret: harbor_password
-      - registry: https://index.docker.io/v1/
-        username:
-          from_secret: docker_username
-        password:
-          from_secret: docker_password
       tags:
       - ${CI_COMMIT_SHA}
       - latest
@@ -147,11 +132,6 @@ steps:
           from_secret: harbor_username
         password:
           from_secret: harbor_password
-      - registry: https://index.docker.io/v1/
-        username:
-          from_secret: docker_username
-        password:
-          from_secret: docker_password
       tags:
       - ${CI_COMMIT_SHA}
       - latest