Demand int32 type for node index when importing vmap data.

This change was necessary as pandas-2.0.0 will handle the dtype for pd.Index
correctly.

Signed-off-by: Johannes Mueller <johannes.mueller4@de.bosch.com>

tests/vmap/reference_data.py

@@ -21,7 +21,7 @@
                    [5., 30., 0.],
                    [10., 30., 0.]]),
     columns=['x', 'y', 'z'],
-    index=pd.Index(np.arange(1, 19), name="node_id")
+    index=pd.Index(np.arange(1, 19), name="node_id", dtype=np.int32)
 )
 
 beam_2d_squ_mesh_index = pd.MultiIndex.from_arrays(