fix(ci): correct image for generating slate docs

.woodpecker/docs.yml

@@ -26,8 +26,7 @@ pipeline:
     # Slate requires a specific directory to run in
     directory: '/srv/slate'
     commands:
-      - echo "$PWD"
-      - mv "$CI_WORKSPACE/docs/api" /srv/slate/source
+      - mv "$CI_WORKSPACE/docs/api" source
       - bundle exec middleman build --clean --watcher-disable
       - mv build "$CI_WORKSPACE/docs/api-build"