[third_party/pigweed] Roll 6 commits

af237dbf10c3843 docs: Split the style guide: commit style
9335766691d9ddd docs: Update module docs authoring guidelines
e1835d3d9149ec6 pw_rpc: Update Java service error with tip
20b5cd27bfe54bc bazel: Move Kythe copts to toolchain configuration
dcaf9148da1ad26 docs: Fix nav and main content scrolling
90f350d0ea40d86 pw_presubmit: Add basic CSS formatter

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 3cabebf8a147672..af237dbf10c3843
Roller-URL: https://ci.chromium.org/b/8765460735505360433
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I403b2b3a3ecd8e510b4199a276c69e5c857c0211
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/kudzu/+/178835
Commit-Queue: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
Bot-Commit: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
diff --git a/third_party/pigweed b/third_party/pigweed
index 3cabebf..af237db 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 3cabebf8a1476729a1fa66047760c7292e183c42
+Subproject commit af237dbf10c3843a006c789a7c40ea250dab68fa