On her way to see a room for rent in Richmond late last year, Lilly Palma waited about 40 minutes for the 71 bus. She crossed the neighborhood off her list. It was “super unwalkable,” Palma said, “and lacked bus stops.” Service on some of Richmond’s bus lines could get thinner if voters reject The Regional Tax Measure on Tuesday, according to a contingency plan drawn up by AC Transit. The regional measure would add a half-cent sales tax in…