Check if in 256-color mode, text output flashes in windows terminal

[aremmell]

I noticed this using the ANSI macros, specifically the one that sets fg and bg simultaneously in 256-color mode, so I'm concerned that libsir might have the same bug.

The fix is to just remove the 4[89];5 entirely and only put 48 in there when you intend to set the background color. Otherwise, it seems like Windows Terminal is interpreting that trailing 5 as a flashing text command.