Users.md: remove wxFormBuilder

according to commit wxFormBuilder/wxFormBuilder@8a3d169

docs/markdown/Users.md

@@ -145,7 +145,6 @@ format files
  - [VMAF](https://github.com/Netflix/vmaf) (by Netflix), a perceptual video quality assessment based on multi-method fusion
  - [Wayland](https://github.com/wayland-project/wayland) and [Weston](https://github.com/wayland-project/weston), a next generation display server
  - [wlroots](https://github.com/swaywm/wlroots), a modular Wayland compositor library
- - [wxFormBuilder](https://github.com/wxFormBuilder/wxFormBuilder), RAD tool for wxWidgets GUI design
  - [xi-gtk](https://github.com/eyelash/xi-gtk), a GTK+ front-end for the Xi editor
  - [Xorg](https://gitlab.freedesktop.org/xorg/xserver), the X.org display server (not the default yet)
  - [X Test Suite](https://gitlab.freedesktop.org/xorg/test/xts), The X.org test suite