[roll third_party/pigweed] pw_log: Make TODO actionable

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/209571
Lint: Lint 🤖 <android-build-ayeaye@system.gserviceaccount.com>

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 47018e2757e4c2c..4d868e624a68d16
Roller-URL: https://ci.chromium.org/b/8748292547511555553
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I7da8ad41474f143b3f542f45f113932d4bca5996
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/examples/+/209556
Bot-Commit: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
Commit-Queue: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
Lint: Lint 🤖 <android-build-ayeaye@system.gserviceaccount.com>
diff --git a/third_party/pigweed b/third_party/pigweed
index 47018e2..4d868e6 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 47018e2757e4c2c6d21c371f074bd862897b8843
+Subproject commit 4d868e624a68d16d65b623bc53b4c802277b26fd