Remove unused tslib function
Flagged during compilation

[22/27] Compiling C object pandas/_libs/tslib.cpython-310-x86_64-linux-gnu.so.p/meson-generated_pandas__libs_tslib.pyx.c.o
  pandas/_libs/tslib.cpython-310-x86_64-linux-gnu.so.p/pandas/_libs/tslib.pyx.c:27000:18: warning: '__pyx_f_6pandas_5_libs_5tslib__array_with_unit_to_datetime_object_fallback' defined but not used [-Wunused-function]

nice! Thanks @WillAyd 