egl: drop incorrect pkg-config file for glvnd

With b01524ff

 ("meson: don't build libGLES*.so with GLVND")
we dropped the incorrect pkg-config files for GLES*.

Since then, the glvnd issue of its missing files has become painfully
apparent, since it break the build for everyone using glvnd.

NVIDIA has had a fix for a few years now, but has yet to accept it:
https://github.com/NVIDIA/libglvnd/pull/86

Since the breakage is already there, let's clean up everything on our side
while we wait for NVIDIA to accept the fix.

Signed-off-by: Eric Engestrom <eric.engestrom@intel.com>
Reviewed-by: Matt Turner <mattst88@gmail.com>