Partially remove workaround for DevCom-1559808

[frederick-vs-ja]

Unblocks one libcxx test for MSVC.

I found that DevCom-1559808 is fixed during working on _STD-/_RANGES-qualifying _Ugly function names.
(And I've realized that structured bindings for pair/subrange involve ADL, so I'm planning changing the return type of _Partition_by_median_guess_common to something like meow_result).

Edit: I was wrong. DevCom-1559808 isn't totally fixed.

Edit: I've filed DevCom-10452846 "Customized structured binding of subrange that refers to dynamic buffer incorrectly causes constant evaluation failure" for the remain issue.

[CaseyCarter]

What's here is good, but it's incomplete. DevCom-1559808 is closed as "fixed", so we need to remove any and all transition comments citing that bug. If we don't, we have TRANSITION comments waiting to respond to an event that is never going to happen. In practice that means we need to rereduce the issue that the remaining workaround in <algorithm> avoids, file that repro as a new DevCom bug, and update the bug number in the TRANSITION comment.

[StephanTLavavej]

Thanks! The "no workaround" / "workaround" system is so great for making these changes easy to review.

[CaseyCarter]

I'm mirroring this to the MSVC-internal repo - please notify me if any further changes are pushed.

[CaseyCarter]

Thanks for helping to keep the code clean of workarounds for fixed bugs.