Typo when setting the xy resolution in `abel/wrappers/wake_t/wake_t_wrapper.py::run_single_step_wake_t`

[ben-c-2013]

ABEL/abel/wrappers/wake_t/wake_t_wrapper.py

Line 369 in 5f5c13e

wakeT_xy_res = 0.1*beam.bunch_length()

The xy-resolution should not be based on the bunch length, but rather on the smallest of x or y beam size.