Truncated last row, suspect one too many added

[shaddybaddah]

Describe the bug
Connecting to a ttyd instance, in a maximized Firefox window (Firefox as obtained via Microsoft Store), the terminal size is adjusted correctly.

In my specific situation, with Firefox menu bars and toolbars, the vertical height calculation considerations being made by ttyd is resulting in 63 rows.

However, this appears to be one too many, as I am getting truncation on the final row.

To Reproduce
Steps to reproduce the behavior:

1. Ensure you have a stock Windows 10 desktop, with the taskbar not hidden and only a single row of default sized icons
2. Install Firefox from Microsoft Store
3. Run ttyd bash on your local Linux server
4. Run and maximise Firefox on a 1920x1080 display
5. Navigate to your ttyd instance within Firefox
6. Expect that the calculated size of the virtual terminal is 270x63
7. Run the following command to get you to the ultimate line: i=2; while [ $i -lt 63 ]; do echo $i; i=$(($i + 1)); done
8. Type some y and p, and any other "dangly" characters you like, and note the truncation of the bottom portion of your characters

Expected behavior
No truncation should occur

Screenshots
Added two screenshots. At the bottom of each is the top part of the Windows 10 taskbar. The entire taskbar not provided just to reduce the opportunity of revealing too much.

Environment:

• OS: Windows 10
• Browser: Firefox as from the Microsoft Store

Additional context
Add any other context about the problem here.