cl_doubletapdelay

The cl_doubletapdelay sets the delay between keypresses required to be a double-tap.

Usage:
/seta cl_doubletapdelay 1
then do:
/vid_restart

Values: – 350 +
Default: “350” (going prone while crouching with double tap)

Note:
It can be annoying so better turn it longer (350 or more).