[roll third_party/pigweed] pw_result: Add dereference operators

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/55304

third_party/pigweed Rolled-Commits: daed5a96e0fa0d6..518f7c16df0b68c
Roller-URL: https://ci.chromium.org/b/8839880645591028048
Cq-Cl-Tag: roller-builder:pigweed-experimental-roller
Cq-Cl-Tag: roller-bid:8839880645591028048
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: Ieff4901ec1e71ff7eff33ea89852297747439574
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/56021
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 daed5a9..518f7c1 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit daed5a96e0fa0d62e25d25accc94a059d68e47e9
+Subproject commit 518f7c16df0b68cc68cb8821ec3e234f45a2ee4c