[roll third_party/pigweed] build: Drop C++14 compatibility from the build and docs

Pigweed no longer supports C++14. C++17 or newer is required. Remove
references to C++14 from the docs and remove some pw_polyfill C++14
functionality.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/177610

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: af57fad456ce3b6..1355e5b8a5ad1e2
Roller-URL: https://ci.chromium.org/b/8766205387079070625
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: Ie745796a45c4e7f4969046954f7c8289954e709a
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/kudzu/+/177809
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 af57fad..1355e5b 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit af57fad456ce3b69a35dee70367e19e964509459
+Subproject commit 1355e5b8a5ad1e221135b69fecb210ba2b449f03