roll: third_party/pigweed f45f0c7..6847cb3 (6 commits)

6847cb3:https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/316452 pw_kernel: Fix riscv `mscratch` handling for userspace
52cb5cc:https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/316113 pw_async2: Cleanup guides.rst further
053ea03:https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/316114 pw_async2: Terminate codelab when main() exits
99a1be7:https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/316453 doxygen: Migrate pw_string
6d939d5:https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/316373 doxygen: Migrate pw_stream
78fce81:https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/311136 docs: Fix Sense automation page

Rolled-Repo: https://pigweed.googlesource.com/pigweed/pigweed
Rolled-Commits: f45f0c728d9f2d..6847cb3dff01db
Roll-Count: 1
Roller-URL: https://cr-buildbucket.appspot.com/build/8705343962824137009
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I181dba2a2e46288e244cb89f930420ad042d40b9
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/examples/+/316674
Lint: Lint 🤖 <android-build-ayeaye@system.gserviceaccount.com>
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 f45f0c7..6847cb3 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit f45f0c728d9f2d5675f2e5fae5b054ecb5091921
+Subproject commit 6847cb3dff01db956b96fd6efc39e667f7ea5c8f