[roll third_party/pigweed] pw_rpc: Update docs to support concurrent calls

This restriction was removed by the support for current
calls added in afaacb6.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/110991

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 8abcfa737cc695f..09eec45d0844b8a
Roller-URL: https://ci.chromium.org/b/8802550918349451585
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I0f6a13cbff819b3e47fd5d7e9c135769d9f60365
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/111010
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 8abcfa7..09eec45 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 8abcfa737cc695f3d02abe6f793bd15348197339
+Subproject commit 09eec45d0844b8a1f8396730268a178b03b076e3