roll: third_party/pigweed pw_thread: Delete unused constructor implementations

Remove implementations of the deprecated function pointer constructor,
which is private and unused.

Original-Bug: b/367786892
Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/236892
Presubmit-Verified: CQ Bot Account <pigweed-scoped@luci-project-accounts.iam.gserviceaccount.com>
Original-Revision: 39f64a722bd24730d936d9360f232a90d699f8a3

Rolled-Repo: https://pigweed.googlesource.com/pigweed/pigweed
Rolled-Commits: 30bdace4866039..39f64a722bd247
Roller-URL: https://ci.chromium.org/b/8735259705458517313
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I26193292efb98e545b858e44797af2ef409c6254
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/238866
Lint: Lint 🤖 <android-build-ayeaye@system.gserviceaccount.com>
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 30bdace..39f64a7 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 30bdace4866039e26a05f8baa379630e066ad660
+Subproject commit 39f64a722bd24730d936d9360f232a90d699f8a3