added onsite projection slicing

src/grogu_magn/core.py

@@ -275,17 +275,3 @@ def onsite_projection(matrix, idx1, idx2):
     """
 
     return matrix[..., idx1, :][..., idx2]
-
-
-def onsite_projection(matrix, idx):
-    """_summary_
-
-    Args:
-        matrix (_type_): _description_
-        idx (_type_): _description_
-
-    Returns:
-        _type_: _description_
-    """
-
-    return matrix[..., idx, :][..., idx]