shader_runner: replace NamedBufferSubdata
This method is not available on any OpenGL ES, so for compatibility it would be better to avoid it.
Initially I thought about adding another wrapper at shader_runner_gles_workarounds, but that seemed an overkill for just one usage of such method. Additionally NamedBufferSubdata requires OpenGL 4.5 or ARB_direct_state_access, so replacing such call would be useful also when testing old versions of OpenGL.