[roll third_party/pigweed] pw_string: Revise front page content

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/140490

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: d3ac9bae83b4e27..3b7c6b71d574191
Roller-URL: https://ci.chromium.org/b/8778819990630272449
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: Id5d8cfc5cbeb3b723ccd3497f226bb851223e72b
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/151041
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 d3ac9ba..3b7c6b7 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit d3ac9bae83b4e278f48221d75aa93c063ba7e7a9
+Subproject commit 3b7c6b71d57419171824f1fe68500960bc49ceb3