Roll external/spirv-headers/ 6a55fade6..4995a2f27 (8 commits)

https://github.com/KhronosGroup/SPIRV-Headers/compare/6a55fade62de...4995a2f2723c

$ git log 6a55fade6..4995a2f27 --date=short --no-merges --format='%ad %ae %s'
2022-03-03 nikita.kornev Remove extensions tag from instructions
2022-02-18 nikita.kornev Implement SPV_KHR_uniform_group_instructions extension
2022-02-12 ben.ashbaugh update SPIR-V headers for SPV_INTEL_split_barrier
2022-02-08 prokop regenerate headers
2022-01-31 gleese Add EXT tag to capability to DemoteToHelperInvocationEXT
2022-01-28 tdb Reserve enum range for MSP extensions
2022-01-05 prokop regenerate the headers
2022-01-04 prokop Include bool type for C

Created with:
  roll-dep external/spirv-headers

DEPS

diff --git a/DEPS b/DEPS
index 2cfb341..051b2de 100644
--- a/DEPS
+++ b/DEPS
@@ -6,7 +6,7 @@
   'effcee_revision': 'ddf5e2bb92957dc8a12c5392f8495333d6844133',
   'googletest_revision': '25dcdc7e8bfac8967f20fb2c0a628f5cf442188d',
   're2_revision': '0c5616df9c0aaa44c9440d87422012423d91c7d1',
-  'spirv_headers_revision': '6a55fade62dec6a406a5a721148f88a2211cbefa',
+  'spirv_headers_revision': '4995a2f2723c401eb0ea3e10c81298906bf1422b',
 }
 
 deps = {