x11-toolkits/gtk30: remnove unnecessary dependency on multimedia/v4l_compat

• The depednecy was previosuly there to get linux/input.h
• However, with [1] gtk switched to using the shipped dev/evdev/input.h on FreeBSD.

[1] https://gitlab.gnome.org/GNOME/gtk/-/commit/7fed0b74ed9f

PR: 253434
Reported by: Oleh Vinichenko <moonlapse81@gmail.com>