FontAwesome 6 upgrade: followup items

[chalin]

Followup to:

• #1102

Tasks:

• [x] #1169
• [x] #1170
• [x] Mention the breaking change in the CHANGELOG
  • For a link to add, see https://github.com/google/docsy/pull/1102#issuecomment-1212520943.
  • #1186
• [ ] #1165

[chalin]

@samiahmedsiddiqui - let me know if you'd like to tackle some of these tasks.

[samiahmedsiddiqui]

@chalin PR created for #1170, I will try to create a PR for #1169 tomorrow.

[chalin]

Wonderful! I think that for #1169, all we might need to do is change the order of the listed fonts (at least that was what I was going to try :).

[chalin]

@samiahmedsiddiqui - FYI, I've submitted a fix for #1169 via #1179.