[roll third_party/pigweed] docs: Add favicon to pigweed.dev

Tested by building the docs locally and verifying the favicon is shown.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/109078

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 97a1fc5a3f81f1b..1ad00fe8f5f9ab4
Roller-URL: https://ci.chromium.org/b/8804085893511403121
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I794a21605cce210e04c0fa9e28a0a2e6bf71428d
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/109086
Commit-Queue: Pigweed Integration Roller <pigweed-integration-roller@pigweed.google.com.iam.gserviceaccount.com>
Bot-Commit: Pigweed Integration Roller <pigweed-integration-roller@pigweed.google.com.iam.gserviceaccount.com>
diff --git a/third_party/pigweed b/third_party/pigweed
index 97a1fc5..1ad00fe 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 97a1fc5a3f81f1bfbda6b9304496a90ca6e3274f
+Subproject commit 1ad00fe8f5f9ab4748f7a97b377b2b36f59528d3