[roll third_party/pigweed] pw_tokenizer: Adjust rustdocs deps to only be in std environments

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/188138

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 0df2560002f2cc4..463799bf5fa059c
Roller-URL: https://ci.chromium.org/b/8758614965876072273
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I56b19b580f3f05f3af39b2b34c86b41a61d83603
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/188210
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 0df2560..463799b 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 0df2560002f2cc471bcf880deabc8030c6206bd8
+Subproject commit 463799bf5fa059c1c2dd1e89246dcf8227248990