[roll third_party/pigweed] Revert "roll: clang"

This reverts commit 7a9b71ad0a5436e9b78998402fe1ad71007a7cd9.

Reason for revert: This roll has a known issue with FlatMap template params. Reverting the auto roll.

Original change's description:
> roll: clang
>
> From: git_revision:c58bc24fcf678c55b0bf522be89eff070507a005
> To: git_revision:ca260e1b119b043195158098a9afda3967c6854b
> Roller-URL: https://ci.chromium.org/b/8755188484734766849
> CQ-Do-Not-Cancel-Tryjobs: true
> Change-Id: Ic97ab8328c4ff35a75d605fd1ed002132a573510
> Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/193790
> Bot-Commit: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
> Commit-Queue: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>

# Not skipping CQ checks because original CL landed > 1 day ago.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/193890

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 154897dd5f6d239..544a7b57c35e116
Roller-URL: https://ci.chromium.org/b/8755057188832926577
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I047216c470ce11151a3c70e3675667b80de5d341
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/examples/+/193931
Commit-Queue: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
Bot-Commit: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
diff --git a/third_party/pigweed b/third_party/pigweed
index 154897d..544a7b5 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 154897dd5f6d2390577e6a29e15bcacfeab7c385
+Subproject commit 544a7b57c35e11690c73c390625a86a9e9a3ae51