[roll third_party/pigweed] roll: buildifier

From: version:2@4.0.1
To: version:2@4.2.1

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/60640
Bot-Commit: Pigweed Roller <pigweed-roller@pigweed.google.com.iam.gserviceaccount.com>

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: df593315e3fde8f..c21847f0d5cd742
Roller-URL: https://ci.chromium.org/b/8836259310186810577
Cq-Cl-Tag: roller-builder:pigweed-sample-project-roller
Cq-Cl-Tag: roller-bid:8836259310186810577
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: Ia74c376826c72169c314b9314354c32d19e8f7e8
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/sample_project/+/60681
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 df59331..c21847f 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit df593315e3fde8fd75b0c094e1a87802c1e1a33a
+Subproject commit c21847f0d5cd7427cee53469a1df33d2e27f351e