Consider consolidating local & express bus TAPs

[nmpeterson]

A remnant of the conventional vs. premium transit split in the original ABM, any node in the highway network that serves as a stop for both local (B, L, P) and express (E, Q) bus modes is currently represented by two TAPs: one for "conventional" service and one for "premium".

Since the ABM is now configured to bypass conventional transit and treat all transit demand equally, these duplicate nodes are likely unnecessary. Consolidating them could improve model runtime and filesize.