roll: third_party/pigweed pw_build: Fix pw_python_venv generated requirements

pw_python_venv was always adding the //pw_build/py gn target to the
list of dependencies to base the generated requirements on. This is
usually not an issue if pw_build is included. However if it isn't
needed extra 3p deps were always getting added from pw_build
regardless.

For example if a venv only needed //pw_docgen/py and //pw_status/py
the generated_requirements would include all these extra packages due
to pw_build being added in along with all their 3p deps:

  //pw_arduino_build/py:py
  //pw_build/py:py
  //pw_cli/py:py
  //pw_config_loader/py:py
  //pw_docgen/py:py
  //pw_env_setup/py:py
  //pw_package/py:py
  //pw_presubmit/py:py
  //pw_status/py:py
  //pw_stm32cube_build/py:py

This change fixes it so only these two are added:

  //pw_docgen/py:py
  //pw_status/py:py

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/240792
Original-Revision: 87f43fec003b4befd74b2362962a76dff7105253

Rolled-Repo: https://pigweed.googlesource.com/pigweed/pigweed
Rolled-Commits: 29fc404197899d..87f43fec003b4b
Roller-URL: https://ci.chromium.org/b/8734687646195417345
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I4e722c19523147486c4a047a0779d23acb599d35
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/examples/+/240622
Commit-Queue: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
Lint: Lint 🤖 <android-build-ayeaye@system.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 29fc404..87f43fe 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 29fc404197899dd272320c336f944b91e2140f09
+Subproject commit 87f43fec003b4befd74b2362962a76dff7105253