[roll third_party/pigweed] pw_presubmit: Make gn_docs_build accessible

Add the gn_docs_build step to the OTHER_CHECKS program so it can be
invoked with --step.

Also have it install nanopb.

Original-Bug: b/285350808
Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/150133

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 98f2c3ba16ba1af..09129c41b616109
Roller-URL: https://ci.chromium.org/b/8779368594393088353
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: Id45272844d3c397830c9b4227d65b73d2599e293
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/150282
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 98f2c3b..09129c4 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 98f2c3ba16ba1af1984ed6dacd998b785fa9acc1
+Subproject commit 09129c41b6161093572958ad0d29df3df20cbf8e