Manually roll spirv-headers

https://chromium.googlesource.com/external/github.com/KhronosGroup/SPIRV-Headers.git/+log/af64a9e826bf..dc77030acc9c

The spirv-tools autoroller didn't roll this repo.

Bug: 1044061
Change-Id: I80878e58d3655f3ed42eb28664d05e101d2a9f77
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2014982
Auto-Submit: Shahbaz Youssefi <syoussefi@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Cr-Commit-Position: refs/heads/master@{#734117}

DEPS

@@ -300,7 +300,7 @@ vars = {
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling feed
   # and whatever else without interference from each other.
-  'spv_headers_revision': 'af64a9e826bf5bb5fcd2434dd71be1e41e922563',
+  'spv_headers_revision': 'dc77030acc9c6fe7ca21fff54c5a9d7b532d7da6',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling feed
   # and whatever else without interference from each other.