roll: third_party/pigweed pw_allocator: Remove SynchronizedAllocatorForTest

This class removes a testing utility type that was added for
pw_multibuf, as it is redundant with a SynchronizedAllocator
that wraps an AllocatorForTest.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/264698
Presubmit-Verified: CQ Bot Account <pigweed-scoped@luci-project-accounts.iam.gserviceaccount.com>
Original-Revision: c48adeb92ff36577a34f22cf7b2a0b8d0086a3b2

Rolled-Repo: https://pigweed.googlesource.com/pigweed/pigweed
Rolled-Commits: 063865c350a7a7..c48adeb92ff365
Roll-Count: 1
Roller-URL: https://cr-buildbucket.appspot.com/build/8723583076606358289
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I5ae1daaac10e50c6468f64749526bba5eb30e464
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/kudzu/+/265856
Lint: Lint 🤖 <android-build-ayeaye@system.gserviceaccount.com>
Bot-Commit: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
Commit-Queue: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
diff --git a/third_party/pigweed b/third_party/pigweed
index 063865c..c48adeb 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 063865c350a7a73aeb0c7fda5c3dc60d91b707e6
+Subproject commit c48adeb92ff36577a34f22cf7b2a0b8d0086a3b2