[roll third_party/pigweed] pw_rpc: Prevent encoding failure when dynamic buffer enabled

- When enable pw_rpc dynamiac buffer is enabled, pwpb encoding could
  fail due to the allocated buffer is too short, adding a offset to
  temporarily bypass the failure

Original-Bug: b/269633514

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/166833

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 5f6d2fcd7ec9b1c..a898f29d6e177db
Roller-URL: https://ci.chromium.org/b/8772491193779865505
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I5f137c26aefee55d7f0de146da4b2ccdd25c9181
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/167070
Bot-Commit: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
Commit-Queue: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
diff --git a/third_party/pigweed b/third_party/pigweed
index 5f6d2fc..a898f29 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 5f6d2fcd7ec9b1ce1fcc6aef5ab7a83e7dba8f63
+Subproject commit a898f29d6e177db2c81b8cae93ccda731599b5d4