AB: AB-16 exit 400 issues

[rickmastfan67]

398 -> 400A, maybe fudge it as 400 to prevent list breakage?
400B -> delete (shouldn't it be counted as part of 'current' exit 400A since it's part of it ramp wise?  Plus, AB-216 doesn't have a separate '54' point for it's connecting ramps.)

NOTE: This will also affect AB TCHYel.

[yakra]

Decade-old GMSV shows it was 398 in the past. Looks like ABMoT tweaked the exit numbers in here for some potential added confusion and little gain. In any case, it's 400A now, so relabeling accordingly. Luckily, 400A is not in use in either AB16 or TCHMai, so no need to worry about a label collision.
Agree re deleting current 400B.

https://github.com/TravelMapping/HighwayData/pull/4270