roll: third_party/pigweed docs: Update changelog for July 2026

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/452352
Original-Revision: 88af1ce547ff9fc197315187a76950fd809c19aa

Rolled-Repo: https://pigweed.googlesource.com/pigweed/pigweed
Rolled-Commits: 7c84c203cbe530..88af1ce547ff9f
Roll-Count: 1
Roller-URL: https://cr-buildbucket.appspot.com/build/8673451631621467185
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I51f7417cc22f180650d0048213208412a2238a24
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/455605
diff --git a/third_party/pigweed b/third_party/pigweed
index 7c84c20..88af1ce 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 7c84c203cbe5301f15f1433215af9a7852432d16
+Subproject commit 88af1ce547ff9fc197315187a76950fd809c19aa