[roll third_party/pigweed] python: Remove setup.py files

`setup.py` files are not required for editable installs anymore. This
s the only reason we kept these files around. Running this works
without them now:

  pip install --editable pw_build/py

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/159472

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 895aaa03a847bca..e1b56dbcd84a836
Roller-URL: https://ci.chromium.org/b/8774489306067569937
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I2eefad8d720893850e239ad4ca44bfaa97d37015
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/159950
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 895aaa0..e1b56db 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 895aaa03a847bca6b5db47f4033ccdd0a671a971
+Subproject commit e1b56dbcd84a836da16f1b34d21edaa157782983