mesa: Enable GL_RGB/GL_RGBA in GLES3 glGetInternalformativ

mesa: Enable GL_RGB/GL_RGBA in GLES3 glGetInternalformativ

Removes commit 7894278 changes and moves fix to _mesa_GetInternalformativ().
The original commit enabled the GL_RGB and GL_RGBA unsized internal formats
as valid for render buffers in GLES3, but this is incorrect. They should
have only been enabled for GetInternalformativ()

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=88079
Reviewed-by: Chad Versace <chad.versace@intel.com>
Reviewed-by: Matt Turner <mattst88@gmail.com>