Fix broken links (closes: #17737)

This MR fixes the broken links pointed out in #17737 (closed).

I found them by running git grep startup_options \*.html and git grep startup_options \*.mdwn in the wiki/src directory.

Closes: #17737 (closed)

Edit: Oh, and I updated the PO files by running:

1. find . -name known_issues.\* -exec sed -i 's/doc\/first_steps\/startup_options\/#boot_loader_menu/doc\/advanced_topics\/boot_options/g' {} + in wiki/src/support

and

2. find . -name graphics.\* -exec sed -i 's/doc\/first_steps\/startup_options\/#boot_loader_menu/doc\/advanced_topics\/boot_options/g' {} + in wiki/src/support/known_issues