Enable ngl gsk renderer for Pinephone

Hi, i have noticed that, for the Pinephone, the GSK_RENDERER env variable enabled to force the use the "gl" renderer. The "ngl" renderer had caused rendering glitches in the past, but seems it is not the case anymore. The issue related to the problem has been fixed and merged: https://gitlab.gnome.org/GNOME/gtk/-/issues/3894 I'm using it daily on my Pinephone that run pmOS Edge and i have not encountered any rendering artifact. The "ngl" render is much faster than the "gl" one and makes applications that rely on gtk4 rendering, like megapixels, much more usable. Picking megapixels as sample application and enabling the "ngl" renderer make it gains a ~3x framerate boost and a reduction of more than half of the cpu usage, leading to a night and day change for a low power device like the Pinephone.

For completeness i will report there was also a bug in lima that, combined with gtk > 4.3.x, leads to rendering artifacts. The problem has been already fixed, but this means that, to avoid the artifacts, mesa should be updated accordingly before shipping gtk > 4.3.x: https://gitlab.freedesktop.org/mesa/mesa/-/issues/5057.

So unlsess i miss something important, i would like to ask to remove/reconsider the introduction of that environment variable (after gtk 4.2, the "ngl" renderer is enabled by default, so there is no need to force it enabled).

I hope i have followed all the rules correctly. If not, i'm sorry, i will fix the problems as soon as possible.

Thanks for listening, Have a good day