fix layout disruption when resizing window with help displayed

[szktkfm]

Summary

close #339

I've fixed the issue where resizing the window height while the help is displayed no longer disrupts the layout. This is a fix for issue #339.

How did you test this change?

Manually tested by resizing the terminal window with the help view open.

Images/Videos

https://github.com/dlvhdr/gh-dash/assets/27483768/b119812c-080f-4c3a-9bcf-8707e177661d