SPIR-V 1.4 test fixes

SPIR-V 1.4 test fixes

This commit fixes a couple of SPIR-V 1.4 tests that had inconsistent
requirements in the Amber script and in the CTS side. In one case we're
dropping the requirement from Amber and in the other one we're adding
the requirement to CTS.

Affected tests:
dEQP-VK.spirv_assembly.instruction.spirv1p4.opptrnotequal.variable_pointers_vars_wg_not_equal
dEQP-VK.spirv_assembly.instruction.spirv1p4.hlsl_functionality1.member_decorate_string

Components: Vulkan
VK-GL-CTS issue: 2958

Change-Id: If1e58bc028ce3756623a241bb259024ef077c815