[roll third_party/pigweed] pw_presubmit: Use autodoc for context classes

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/169119

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 9e20d2f98b6a279..406106bd94039fb
Roller-URL: https://ci.chromium.org/b/8768241430093659089
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I0ccffc3a47d80e164994124ad32913d3c36abc1f
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/174033
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 9e20d2f..406106b 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 9e20d2f98b6a2792ce912cf79dc80133e924bd0c
+Subproject commit 406106bd94039fb28cf12e5eb4949bbf5bba31ae