[third_party/pigweed] Roll 2 commits

ad9855ce2a6b9ef pw_log_android: Add pw_log_android_stderr
6484e183fe1afbe pw_log_android: Add module documentation

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 71ad8f01f5735ae..ad9855ce2a6b9ef
Roller-URL: https://ci.chromium.org/b/8753414212730710017
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: Ib309a107e51d80f7125ea74a8ee5f42f5bb3fb57
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/examples/+/197050
Bot-Commit: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
Commit-Queue: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
diff --git a/third_party/pigweed b/third_party/pigweed
index 71ad8f0..ad9855c 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 71ad8f01f5735ae257961526ff3733ef47427bf4
+Subproject commit ad9855ce2a6b9ef0e5e848d1a772689e69bb9690