Installing Pandasgui breaks opencv/matplotlib compatibility

Ubuntu 20.04.5 LTS

To reproduce:

Install matplotlib, and opencv, then install pandasgui. Note that you can no longer plot anything with matplotlib due to the following error:

```
QObject::moveToThread: Current thread (0x2c2de30) is not the object's thread (0x36f3050).
Cannot move to target thread (0x2c2de30)

qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "/.../venv/lib/python3.8/site-packages/cv2/qt/plugins" even though it was found.
This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may fix this problem.

Available platform plugins are: xcb, eglfs, linuxfb, minimal, minimalegl, offscreen, vnc, wayland-egl, wayland, wayland-xcomposite-egl, wayland-xcomposite-glx, webgl.

Process finished with exit code 134 (interrupted by signal 6: SIGABRT)
```

I suspect this is because pandasgui installs PyQT5 as a dependency, breaking opencv/matplotlibs dependence on QT installed on the system. Pandasgui should handle this gracefully and make use of existing backends rather than force-installing PyQT5.