main/postmarketos-base-mesa: add mesa-gles (MR 5654)

Since mesa upgrade from 24.0.9 to 24.1.2 PulseAudio Volume Control
"pavucontrol" needs "mesa-gles" to start on some devices. There is no
direct dependency, however. Instead it's "libepoxy", a Direct Rendering
Manager runtime library, that calls the necessary mesa library.

Other than user interface MATE, where e.g. "mate-session-manager" draws
in "mesa-gles", and other than mesa packages like "mesa-gl" that gets drawn
in by e.g. "xorg-server", there is no direct connection between Xfce4 and
"mesa-gles".

Adding package "mesa-gles" to "postmarketos-base-mesa" is a straightforward
fix for this issue.

Fixes #3042
[ci:skip-build]: already built successfully in CI