[roll third_party/pigweed] pw_build: Restore previous Mypy default behavior

The --namespace-packages option is enabled by default starting in Mypy
0.991. This caused mypy to incorrectly resolve module names for some
source files on a few systems.

This changes restores the previous default mypy behavior by disabling
namespace packages.

Original-Bug: b/265836842
Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/126672

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: f9864011d50c2f1..595ea383848eb3a
Roller-URL: https://ci.chromium.org/b/8791683748354332833
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I0ba0b0b7ad73dcfa88aee04f4796b850bff02012
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/126660
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 f986401..595ea38 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit f9864011d50c2f10f091f856f03b49c113bb5b5b
+Subproject commit 595ea383848eb3a43e845fef4e7cf02909a6b702