[roll third_party/pigweed] pw_rust: Remove variables and declare directly

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/151133

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 7dcae30e225b26c..5d2525d92d5bc4f
Roller-URL: https://ci.chromium.org/b/8778452461725217457
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I3e44367c80b6e89a5614470f21c1beb67f9f2b4b
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/151535
Commit-Queue: Pigweed Integration Roller <pigweed-integration-roller@pigweed.google.com.iam.gserviceaccount.com>
Bot-Commit: Pigweed Integration Roller <pigweed-integration-roller@pigweed.google.com.iam.gserviceaccount.com>
diff --git a/third_party/pigweed b/third_party/pigweed
index 7dcae30..5d2525d 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 7dcae30e225b26c16f59f8ee32d62480f803c425
+Subproject commit 5d2525d92d5bc4fd5e45bedfed9da6f3a0adf5f3