docs(mac): fix T1 chip model identifiers and remove non-Touch Bar A1708

[agush22]

Summary

Corrects inaccurate model mappings in mac-support.md:

• Fixes A1706 port count (4 Thunderbolt 3 ports, Touch Bar).
• Removes A1708 (2 Thunderbolt 3 ports, physical function keys) from the T1 list as it does not contain a T1 chip.
• Clarifies that A1706 and A1707 cover both 2016 and 2017 Touch Bar generations.

[omarchybot]

Reviewed at 630f172 against quattro. It changes only manual/44-mac-support.md, and that section is unchanged on quattro since this branch forked.

The corrections are right. A1706 is the 13-inch Touch Bar model with four Thunderbolt 3 ports, from 2016 and 2017. The page had swapped its port count with A1708's. A1708 is the two-port model with function keys, which has neither a Touch Bar nor a T1, so removing it is correct. A1707 is the 15-inch Touch Bar model, also from 2016 and 2017. Nothing in the installer keys on these model numbers: install/hardware/apple/ matches on MacBookPro13,x and MacBookPro14,x, and those cover both generations. No other open pull request changes this section. #13532 edits the same file, but a different section.

Checked by Claude Opus 5.5. The second opinion (Codex Medium) did not run because the day's review budget was already spent, so this has not been labelled verified or ready. It is waiting on the maintainer.