[third_party/pigweed] Roll 3 commits

a29bf57c735c7c7 pw_span: Follow new module docs guidelines
856491408766e7d pw_ide: Fix VSC extension build command
749043357bc3303 pw_ide: Improve Python `--install-editable`

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 06aca398f331735..a29bf57c735c7c7
Roller-URL: https://ci.chromium.org/b/8759064970201486065
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I7a7904be207ffed003e5b69600a433ef0fffedef
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/187773
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 06aca39..a29bf57 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 06aca398f33173563f434644765a80275d5b6a94
+Subproject commit a29bf57c735c7c787694167d063174f49192a8c6