[lldb] Fix a bug when disabling the statusline. (#169127)
Currently, disabling the statusline with `settings set show-statusline
false` leaves LLDB in a broken state. The same is true when trying to
toggle the setting again.
The issue was that setting the scroll window to 0 is apparently not
identical to setting it to the correct number of rows, even though some
documentation online incorrectly claims so.
Fixes #166608
