[roll third_party/pigweed] pw_rpc: Replace existing client calls in RegisterCall

This updates the RPC client to replace (cancel) an existing call when a
new one is started for the same RPC instead of failing. This is
consistent with the Python client and expected user behavior (calling an
RPC with the same context should replace the first).

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/60820

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 5ebdaeb1d246dc8..2a02c511260e7d0
Roller-URL: https://ci.chromium.org/b/8836146352795810593
Cq-Cl-Tag: roller-builder:pigweed-sample-project-roller
Cq-Cl-Tag: roller-bid:8836146352795810593
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I72186ef73c3cf0635581274763b0df15a5ad1aa5
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/sample_project/+/60840
Bot-Commit: 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 5ebdaeb..2a02c51 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 5ebdaeb1d246dc8f1bff83a35b733a63121322c1
+Subproject commit 2a02c511260e7d0651de4fccc9cf0d1d2fa8b6cc