roll: third_party/pigweed pw_env_setup: Upgrade to Sphinx v7.4.7

We need v7.4.7 (the last v7 release) to use the new Sphinx
features that were introduced in rules_python v0.36.0. These
features will be the foundation of our Bazel-based docs build
system. The new rules_python features introduced in v0.36.0
don't work with the version of Sphinx that we're currently
on (v7.1.2).

Original-Bug: 318892911
Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/238553
Presubmit-Verified: CQ Bot Account <pigweed-scoped@luci-project-accounts.iam.gserviceaccount.com>
Original-Revision: 9a5296672be32b32d684e5250b0c688ceb9206ea

Rolled-Repo: https://pigweed.googlesource.com/pigweed/pigweed
Rolled-Commits: 53b16cd8d29078..9a5296672be32b
Roller-URL: https://ci.chromium.org/b/8735083197769323681
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I32071ffbc24cb862991980071fa5d701210e43be
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/examples/+/239792
Lint: Lint 🤖 <android-build-ayeaye@system.gserviceaccount.com>
Bot-Commit: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
Commit-Queue: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
diff --git a/third_party/pigweed b/third_party/pigweed
index 53b16cd..9a52966 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 53b16cd8d2907855b13bec9159286927de602a72
+Subproject commit 9a5296672be32b32d684e5250b0c688ceb9206ea