Roll external/spirv-headers/ b765c355f..5a1218669 (1 commit)

https://github.com/KhronosGroup/SPIRV-Headers/compare/b765c355f488...5a121866927a

$ git log b765c355f..5a1218669 --date=short --no-merges --format='%ad %ae %s'
2022-05-20 waprave Implemented Beef language header generation

Created with:
  roll-dep external/spirv-headers
diff --git a/DEPS b/DEPS
index d84101f..808ef6c 100644
--- a/DEPS
+++ b/DEPS
@@ -6,7 +6,7 @@
   'effcee_revision': 'ddf5e2bb92957dc8a12c5392f8495333d6844133',
   'googletest_revision': '548b13dc3c02b93f60eeff9a0cc6e11c1ea722ca',
   're2_revision': '5723bb8950318135ed9cf4fc76bed988a087f536',
-  'spirv_headers_revision': 'b765c355f488837ca4c77980ba69484f3ff277f5',
+  'spirv_headers_revision': '5a121866927a16ab9d49bed4788b532c7fcea766',
 }
 
 deps = {