[roll third_party/pigweed] pw_rpc: Use span copy constructor instead of iterator-based one

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/99287

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: a1858e3730f30bf..f76bcef1f4b36cd
Roller-URL: https://ci.chromium.org/b/8810529151297411713
Cq-Cl-Tag: roller-builder:pigweed-experimental-roller
Cq-Cl-Tag: roller-bid:8810529151297411713
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: Ie561e7e476102c38ac595d50acd2032148c82bee
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/99530
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 a1858e3..f76bcef 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit a1858e3730f30bfc4734d3a790d2057d534efff6
+Subproject commit f76bcef1f4b36cd6d890ba3b85d313ea98ac9101