Debug dependencies in features2d

[Stefan Fabian]

The debian package for the features2d module (libopencv-features2d4.2 4.2.0+dfsg-5) on Ubuntu 20.04 has a dependency on the highgui module which is only a debug dependency and should not be a dependency of the release binary.
This dependency indirectly adds dependencies on almost a complete desktop environment which is undesirable on headless systems.
May also be the case for other components.
I have only checked core flann imgproc imgcodecs and features2d of which only features2d includes debug dependencies. Haven't checked the dev versions.