fix: dev docs

Signed-off-by: kj455 <[email protected]>

Author: kj455

docs/content/en/docs-dev/user-guide/plan-preview.md

@@ -38,7 +38,8 @@ pipectl plan-preview \
   --repo-remote-url={ REPO_REMOTE_GIT_SSH_URL } \
   --head-branch={ HEAD_BRANCH } \
   --head-commit={ HEAD_COMMIT } \
-  --base-branch={ BASE_BRANCH }
+  --base-branch={ BASE_BRANCH } \
+  --sort-label-keys={ SORT_LABEL_KEYS }
 ```
 
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