[roll third_party/pigweed] targets: Fix heading levels in each target_docs.rst

Some headings were shown in the left sidebar TOC. This removes those.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/97960

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: c3bdb8abc4bd72b..1b316704ba4b9ec
Roller-URL: https://ci.chromium.org/b/8811427770231660433
Cq-Cl-Tag: roller-builder:pigweed-experimental-roller
Cq-Cl-Tag: roller-bid:8811427770231660433
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I22e1c914aa5821421c0c3f17a4e3f7a6f03ac4b4
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/97954
Commit-Queue: Pigweed Integration Roller <pigweed-integration-roller@pigweed.google.com.iam.gserviceaccount.com>
Bot-Commit: Pigweed Integration Roller <pigweed-integration-roller@pigweed.google.com.iam.gserviceaccount.com>
diff --git a/third_party/pigweed b/third_party/pigweed
index c3bdb8a..1b31670 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit c3bdb8abc4bd72b5f7e9ff8d3e9cfc1f83b9c53d
+Subproject commit 1b316704ba4b9ec57704b843723c512d62b9949b