hwui/debug: Remove glMultiDrawElementsBaseVertexOES stubs.

This function was included by mistake in Khronos OpenGL headers.
See this link for further information:
https://github.com/KhronosGroup/OpenGL-Registry/issues/81

Bug: 32147090
Bug: 66900669
Bug: 72959780
Test: Built and flashed the build onto Pixel XL, ran some CTS tests.
Change-Id: If8f9837466b7d3eb0685624a70b5d5b6fbd86e2e