roll: third_party/pigweed pw_chrono: Don't import individual types in py

Update imports to not import individual types to comply with
python style guide.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/259013
Presubmit-Verified: CQ Bot Account <pigweed-scoped@luci-project-accounts.iam.gserviceaccount.com>
Original-Revision: d93f98687c38ec4d5a5fbd7e68ad1ebe5375de63

Rolled-Repo: https://pigweed.googlesource.com/pigweed/pigweed
Rolled-Commits: aef6fca14a9c0c..d93f98687c38ec
Roll-Count: 1
Roller-URL: https://cr-buildbucket.appspot.com/build/8726258422650256817
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I062db824eb8b417c31cc29fc68345e236370687d
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/259077
Bot-Commit: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
Commit-Queue: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
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diff --git a/third_party/pigweed b/third_party/pigweed
index aef6fca..d93f986 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit aef6fca14a9c0c56eebe3e6c7551d99149e8f3ff
+Subproject commit d93f98687c38ec4d5a5fbd7e68ad1ebe5375de63