Only 'A1' is cleared when clearing a sheet with frozen columns

[karelserruys-foodpairing]

Description

When trying to clear a sheet that has frozen columns and rows, only cell A1 is cleared.
I think it's caused by this line of code:

gspread-pandas/gspread_pandas/spread.py

Line 606 in 60e8d93

self.update_cells(start=(1, 1), end=(1, 1), vals=[""])

Proposed solution

Revert this change: 60e8d93