Fix broken links

[kevinAlbs]

Summary

Fix broken links in Hugo documentation.

This PR includes additional drive-by improvements:

• replace http://mongocxx.org with https://mongocxx.org
• replace mongodb.github.io with mongocxx.org

Background & Motivation

#1039 replaced use of the inline namespace macros with inline namespace v_noabi. I expect this changed the Doxygen page links include the namespace:

Example:

• In 3.8.1: https://mongocxx.org/api/mongocxx-3.8.1/classbsoncxx_1_1oid.html
• In 3.9.0: https://mongocxx.org/api/mongocxx-3.9.0/classbsoncxx_1_1v__noabi_1_1oid.html

This PR is intended as a short-term solution to fix the broken links. Further investigation may be needed to restore links omitting the namespace.

#1026 changed the directory structure. I expect this resulted in broken links to GitHub source pages:

• In 3.8.1: https://github.com/mongodb/mongo-cxx-driver/blob/r3.8.1/src/mongocxx/database.hpp
• In 3.9.1: https://github.com/mongodb/mongo-cxx-driver/blob/r3.9.0/src/mongocxx/include/mongocxx/v_noabi/mongocxx/database.hpp

Broken links were checked by building docs with cmake --build cmake-build --target hugo and running find_broken_links.py.

[kevinAlbs]

Documentation has been updated with cmake --build cmake-build --target hugo-deploy. Merging.