roll: third_party/pigweed b4e8539..ab421e2 (4 commits)

ab421e2:https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/314054 pw_toolchain: Ensure Bazel warnings match GN
e1a57a6:https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/349133 pw_bluetooth_sapphire: Silence -Wshadow violations
e8d3556:https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/349318 workflows.json: Add python linting builds
c4c8c7b:https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/349317 pw_web: Clean up migration shim

Rolled-Repo: https://pigweed.googlesource.com/pigweed/pigweed
Rolled-Commits: b4e85396981f9d..ab421e291f2831
Roll-Count: 1
Roller-URL: https://cr-buildbucket.appspot.com/build/8697095216870242209
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: Ie68c8169299ea3bf522a9c613f14db7dc7be88fb
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/examples/+/349322
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 b4e8539..ab421e2 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit b4e85396981f9d7b019b84e2d06af12f83361e97
+Subproject commit ab421e291f28316fdb926c5c06ddb4da7be3ff89