[roll third_party/pigweed] pw_rpc: Python client updates

- Apply the protobuf function signature to the send method instead of
  the __call__ method for client and bidirectional streaming RPCs.
- Minor type checking improvements.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/53529

third_party/pigweed Rolled-Commits: 876522d0e828fa8..06efdd483be4bf2
Roller-URL: https://ci.chromium.org/b/8840611201265973424
Cq-Cl-Tag: roller-builder:pigweed-experimental-roller
Cq-Cl-Tag: roller-bid:8840611201265973424
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: Icd6e0d4c0108ec56022cdecf0b9914acc58c6082
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/54629
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 876522d..06efdd4 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 876522d0e828fa8f8c08f5078f8ad04fb6ac4ef8
+Subproject commit 06efdd483be4bf288a4e794362bc0ffe723e5a7b