Bold doesn't work for some .xls files

[bondyr3]

• xls2xlsx version: 0.2.0
• Python version: 3.10.4
• Operating System: Windows 10

Description

Certain .xls files won't specify formatting as bold. Instead the sheets use weight = 700.
xls2xlsx only looks at the bold flag and not the font weight value.

[felschatz]

PR exists to fix this issue