fix: pass mixed_type to eval_descriptor in cli (#5177)

Fix #5176.

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## Summary by CodeRabbit

* **Bug Fixes**
* Fixed mixed_type parameter not being properly forwarded during
descriptor evaluation, ensuring the flag is now correctly propagated
through the evaluation process.

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Author: njzjz

deepmd/entrypoints/eval_desc.py

@@ -128,6 +128,7 @@ def eval_desc(
             atype,
             fparam=fparam,
             aparam=aparam,
+            mixed_type=mixed_type,
         )
 
         # descriptors are kept in 3D format (nframes, natoms, ndesc)