CI: migrate from 'plugins/s3:1' to 'woodpeckerci/plugin-s3:latest' (#17234)

- this fixes the CI release upload issues, as the docker image for this is freshly built (unlike the mostly unmaintained "official" drone plugins), thus containing current CA certs needed for letsencrypt since 2021-09-31.
- woodpecker is a drone-ci fork maintained partially by @6543. it's API compatible with current drone plugins afaik

.drone.yml

 
   - name: release-branch
     pull: always
-    image: plugins/s3:1
+    image: woodpeckerci/plugin-s3:latest
     settings:
       acl: public-read
       bucket: gitea-artifacts
         - push
 
   - name: release-main
-    image: plugins/s3:1
+    image: woodpeckerci/plugin-s3:latest
     settings:
       acl: public-read
       bucket: gitea-artifacts
 
   - name: release-tag
     pull: always
-    image: plugins/s3:1
+    image: woodpeckerci/plugin-s3:latest
     settings:
       acl: public-read
       bucket: gitea-artifacts