[Desktop Windowing] Rename Additional Windows Above Status Bar flag.

Renames the flag to "Enable Handle Input Fix" to better describe the
use of the flag, that being to fix input issues in the handle area. Also labels it as a bugfix flag.

Bug: 316186265
Test: m
Flag: NONE, renaming a flag
Change-Id: I7abafcdeca5d4c668d893b069c291d277e5b0359