Fix option name typos in manpages
Fix incorrect spelling of command line options --export-png-antialias
and --export-png-compression. The underscore variant was likely copied
from source code.
I stumbled upon this when converting SVG to PNG:
$ inkscape --version
Inkscape 1.4 (e7c3feb100, 2024-10-09)
$ inkscape --export_png_compression=9 --export_png_antialias=3 -w 192 -h 192 -o icon.png logo.svg
Unknown option --export_png_compression=9