roll: third_party/pigweed 9243851..6422c9a (3 commits)

6422c9a:https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/238189 pw_presubmit: Have docs_build check rust docs
e26be58:https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/238272 pw_tokenizer: Expose API to define new token entry
30dcf2b:https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/237933 pw_metric: Emit valid JSON from Metric::Dump

Rolled-Repo: https://pigweed.googlesource.com/pigweed/pigweed
Rolled-Commits: 92438518417d49..6422c9ae137ad3
Roller-URL: https://ci.chromium.org/b/8735625671811175329
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I2b8bb2f54e317fb04bda0bfa6dee152a3dcd2fd3
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/examples/+/238475
Bot-Commit: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
Commit-Queue: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
Lint: Lint 🤖 <android-build-ayeaye@system.gserviceaccount.com>
diff --git a/third_party/pigweed b/third_party/pigweed
index 9243851..6422c9a 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 92438518417d49c3457090c1b3c57f71007743e8
+Subproject commit 6422c9ae137ad37a9ec172dcd95f294ce5631f82