[roll third_party/pigweed] build: Remove build_pigweed_python_source_tree from default

The build_pigweed_python_source_tree step is fairly slow since it
involves installing Python packages. The step runs for every Python
change. Remove it from the default build target since it doesn't provide
helpful feedback during development.

The build_pigweed_python_source_tree target is still very simple to run:

  ninja -C out pw_env_setup:build_pigweed_python_source_tree

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/60448

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 7b357427a7f6578..d0d3929cce3e9d7
Roller-URL: https://ci.chromium.org/b/8836468510038391857
Cq-Cl-Tag: roller-builder:pigweed-experimental-roller
Cq-Cl-Tag: roller-bid:8836468510038391857
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: Idc95253290bc816a5d6d0f3d608a9f2120b7262e
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/60481
Bot-Commit: Pigweed Integration Roller <pigweed-integration-roller@pigweed.google.com.iam.gserviceaccount.com>
Commit-Queue: Pigweed Integration Roller <pigweed-integration-roller@pigweed.google.com.iam.gserviceaccount.com>
diff --git a/third_party/pigweed b/third_party/pigweed
index 7b35742..d0d3929 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 7b357427a7f6578d3d959622fe1a6c1e402d1e5d
+Subproject commit d0d3929cce3e9d786dcb3dd3e8ebe5501de0805a