We don't support any of the variable pointers capabilities, but we must
accept the extension token.

Bug: b/130937460
Test: dEQP-VK.spirv_assembly.instruction.graphics.pointer_parameter.buffer_memory_variable_pointers_frag
Change-Id: Icb6511b6e1de85c3736e12b4a4e21aa4d1be6622
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/31030Tested-by: Chris Forbes <chrisforbes@google.com>
Presubmit-Ready: Chris Forbes <chrisforbes@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>