[website] Build the man pages for iguana and the proof-manager-cli

Summary: After D18961 we have the target to build the man pages for these new tools. Let's build them so they get added to the online documentation.

Test Plan: Tested locally by heavily massaging the script so it runs against my local tree that include the man page target.

Reviewers: #bitcoin_abc, PiRK

Reviewed By: #bitcoin_abc, PiRK

Differential Revision: https://reviews.bitcoinabc.org/D18963