[roll third_party/pigweed] pw_bytes: Add example to docs of using _b suffix

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/201350

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 18442a7e69a5b1c..f6d9544b2895948
Roller-URL: https://ci.chromium.org/b/8751816562915856081
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I1954c2b0802792aa0031119ac50dfa61ddf332fc
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/201410
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 18442a7..f6d9544 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 18442a7e69a5b1c5794f028b7d98082f58f0475a
+Subproject commit f6d9544b2895948992d0a9213941858db14d5e4b