Fix LTE Timing Advance Doc String

The Doc string for LTE timing advance incorrectly
lists the range based on the maximum size of an
incremental TA command rather than the cumulative
timing advance. The spec reference is correct, but
the range was wrong.

Bug: 66751464
Test: compilation (docstring only change)
Change-Id: I0242cae7af40a7d9ed5ae9a2a509592076e5b6a3