[roll third_party/pigweed] docs: Remove implemented TODOs

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/70280

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 9126569a6877c16..64a4b16be46435f
Roller-URL: https://ci.chromium.org/b/8829828705452554513
Cq-Cl-Tag: roller-builder:pigweed-sample-project-roller
Cq-Cl-Tag: roller-bid:8829828705452554513
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: Ib7f5d23c6a569b03e96f1027435557fce8d34b06
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/sample_project/+/70380
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 9126569..64a4b16 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 9126569a6877c1638aaae763504d171d5d80b587
+Subproject commit 64a4b16be46435f6aacbf29f5fb70c355ff90216