[roll third_party/pigweed] docs: Recommend "Fixed" rather than "Fixes"

Most Pigweed devs (myself included) would rather use "Fixes", but it
doesn't actually work, and the docs should reflect that sad reality.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/69480

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: bcabcd78d99dcd4..d159d5620082a6e
Roller-URL: https://ci.chromium.org/b/8830278752036282497
Cq-Cl-Tag: roller-builder:pigweed-sample-project-roller
Cq-Cl-Tag: roller-bid:8830278752036282497
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: Ie1e6b2d3afa79d8780827e5d2910cd5b1b0b09e2
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/sample_project/+/69680
Bot-Commit: Pigweed Integration Roller <pigweed-integration-roller@pigweed.google.com.iam.gserviceaccount.com>
Commit-Queue: Pigweed Integration Roller <pigweed-integration-roller@pigweed.google.com.iam.gserviceaccount.com>
diff --git a/third_party/pigweed b/third_party/pigweed
index bcabcd7..d159d56 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit bcabcd78d99dcd4763e6d79c0d2459ade8c6348d
+Subproject commit d159d5620082a6eaea0db28f5167d34b46fdb109