Fix run time errors with python3.12 and pyside6 (#13337)

* Change pyopen=open expression to from builtins import open as pyopen

---------

Co-authored-by: Adrián Insaurralde Avalos <36372335+adrianinsaval@users.noreply.github.com>

src/Mod/Spreadsheet/importXLSX.py

@@ -63,9 +63,6 @@ except ValueError:
 else:
     gui = True
 
-if open.__module__ in ["__builtin__", "io"]:
-    pythonopen = open
-
 
 # The sepToken structure is used in the tokenizer functions isKey and
 # getNextToken.