fix: address PR feedback - remove test files and move h5py import

Co-authored-by: njzjz <9496702+njzjz@users.noreply.github.com>

Author: Copilot

deepmd/tf/entrypoints/train.py

@@ -13,6 +13,11 @@
     Optional,
 )
 
+try:
+    import h5py
+except ImportError:
+    h5py = None
+
 from deepmd.common import (
     j_loader,
 )
@@ -244,8 +249,8 @@ def _do_work(
 
             if not Path(stat_file_raw).exists():
                 if stat_file_raw.endswith((".h5", ".hdf5")):
-                    import h5py
-
+                    if h5py is None:
+                        raise ImportError("h5py is required for HDF5 stat files")
                     with h5py.File(stat_file_raw, "w") as f:
                         pass
                 else: