[roll third_party/pigweed] pw_thread_freertos: adjust detach to CHECK joinable

Adjusts the FreeRTOS backend to use PW_CHECK(joinable()) in
detach just like ThreadX's backend.

No-Docs-Update-Reason: No API change.
Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/40666

third_party/pigweed Rolled-Commits: f4da489b23c0396..47941cc13a18e5a
Roller-URL: https://ci.chromium.org/b/8850107189745621552
Cq-Cl-Tag: roller-builder:pigweed-experimental-roller
Cq-Cl-Tag: roller-bid:8850107189745621552
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: Iadc67a1c92dc4022a252f58c06b9bb6a8f1223dc
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/40646
Reviewed-by: 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 f4da489..47941cc 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit f4da489b23c03963af9c82f631674d76f55065b3
+Subproject commit 47941cc13a18e5a20147a89f526731bfa41bbef4