fix bug in download (#148)

The order of `steps` returned by `wf.query_step_by_key` is not
guaranteed.

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Co-authored-by: Sikai Yao <yaosk@dp.tech>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

dpgen2/utils/download_dpgen2_artifacts.py

@@ -190,9 +190,7 @@ def download_dpgen2_artifacts_by_def(
         wf_info = wf.query()
         wf_steps = [wf_info.get_step(key=kk)[0] for kk in step_keys]
     # make step dict
-    step_dict = {}
-    for kk, ss in zip(step_keys, wf_steps):
-        step_dict[kk] = ss
+    step_dict = {wf_step.key: wf_step for wf_step in wf_steps}
 
     # download all items
     for ii in dld_items: