Revert "Don't remove SPV_INTEL_optimization_hints declaration"

This reverts commit 1484d3a.

Author: vmaksimo

llvm-spirv/include/LLVMSPIRVExtensions.inc

@@ -22,7 +22,6 @@ EXT(SPV_INTEL_kernel_attributes)
 EXT(SPV_INTEL_io_pipes)
 EXT(SPV_INTEL_inline_assembly)
 EXT(SPV_INTEL_arbitrary_precision_integers)
-EXT(SPV_INTEL_optimization_hints)
 EXT(SPV_INTEL_float_controls2)
 EXT(SPV_INTEL_vector_compute)
 EXT(SPV_INTEL_fast_composite)