Remove EGL_KHR_image_gl_colorspace workaround for Android P

The ro.vndk.version sysprop is getting removed as part of VNDK
deprecation, which will break this workaround. Android P is not really
supported anymore, so remvoe the workaround entirely.

Bug: 311267616
Test: builds
Change-Id: Ieb65da5504083d2db275a68940c1d83940219505