[roll third_party/pigweed] pw_function: Update example to match guidelines for parameters

https://pigweed.dev/pw_function/#pw-function-as-a-function-parameter
says: "If the pw::Function simply needs to be called, it should be
passed by const reference."

See also: pwrev/67943

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/170651

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: fe6f6848f02f4f3..ab45b0af879939b
Roller-URL: https://ci.chromium.org/b/8770019934678863761
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I9cf239f5e0f5784f54485367a06ef9da24a014f9
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/170826
Commit-Queue: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
Bot-Commit: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
diff --git a/third_party/pigweed b/third_party/pigweed
index fe6f684..ab45b0a 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit fe6f6848f02f4f306ce87700464a1091f80828dc
+Subproject commit ab45b0af879939b0b5a9ba4ceb4e0a35978e60f7