roll: third_party/pigweed 3 commits

3d3846b9188822b pw_boot: Remove backend multiplexer
60532cd8bdd59fe pw_sync: Remove multiplexers
630750e177353d5 pw_cpu_exception_cortex_m: rm backend multiplexer

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: f437033232f7e9b..3d3846b9188822b
Roller-URL: https://ci.chromium.org/b/8744117268117261761
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I2a095035668e0a5e74dda2cc30e4b6f6f40a976d
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/examples/+/218227
Commit-Queue: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
Bot-Commit: 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 f437033..3d3846b 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit f437033232f7e9b77a9f68a73b6369c044fcd248
+Subproject commit 3d3846b9188822b02068a8addcc4677a52cbbcba