Fix excelfile parse dimensions

[matheuszpher]

Closes #63010

Fixes an issue where ExcelFile.parse() with openpyxl resets
Worksheet.max_row and Worksheet.max_column to None.

Changes

Removed the sheet.reset_dimensions() call for read-only sheets,
as it causes unexpected loss of dimension information after parsing.

Reproducible example

import pandas as pd

with pd.ExcelFile("some_file.xlsx") as excel_file:
    ws = excel_file.book["Sheet1"]
    dim_before = (ws.max_row, ws.max_column)
    excel_file.parse(sheet_name=ws.title)
    dim_after = (ws.max_row, ws.max_column)

assert dim_before == dim_after  # now passes ✅

[rhshadrach]

As expressed in the linked issue, I'm negative on this approach.