[roll third_party/pigweed] pw_rpc: Suppress warnings and make method public in Java client

- Suppress ShouldNotSubclass warnings for ListenableFuture, since the
  class is not actually reimplemented.
- There is no need for MethodClient.method() to be package-private, so
  make it public. This was intended to be part of
  https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/126450,
  but was accidentally left out.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/126531

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 7767406bf5a550a..4b6c52dbc6058d2
Roller-URL: https://ci.chromium.org/b/8792038815595757921
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I5b9bd7c0d08351b4f17e71078992a008215079f1
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/126519
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 7767406..4b6c52d 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 7767406bf5a550a115d810232f7bf4344daa147a
+Subproject commit 4b6c52dbc6058d2f9e04f62d654f33c82e88e170