Don't insets the divider bar with task bar when IME showing

There is no need to insets the divider bar with taskbar when IME showing
because there are no rounded corners at the bottom. This also avoids the
problem of task bar height not changing when IME floating.

Bug: 257011088
Test: Manual check the task bar does draw to bottom when IME floating
      and restore when IME hidden.
Change-Id: Iba5bbf5247e34f0063e67ddcd0a0b3deb8f772fb