link-check causing some build errors after 2024 update

[egithinji]

After #2658, cargo xtask build (ormdbook build) is failing with the error mentioned here: Michael-F-Bryan/mdbook-linkcheck#92. This can be fixed by removing the [output.linkcheck] section from book.toml (since I believe we're now using linkcheck2?).

However after that, the exclusions in the [output.linkcheck2] section don't seem to work, and building results in errors like File not found: comprehensive-rust.pdf.

[qwandor]

Having both config sections is necessary for now as a workaround for marxin/mdbook-linkcheck2#2. If this is failing for you locally, try cargo uninstall mdbook-linkcheck to get rid of the old version.

[michael-kerscher]

@egithinji to avoid requiring everyone to do this mitigation, one option could be to extend the xtask install-tools to remove the old linkcheck (but fail silently if is is already removed)