roll: third_party/pigweed: targets/rp2040: Enhance on-device testing instructions

Documents the single-pico workflow, and shifts docs to recommend a Pico
and a Debug Probe rather than the PicoPico, which cannot be purchased.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/225311
Lint: Lint 🤖 <android-build-ayeaye@system.gserviceaccount.com>

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 6afbf6deaa1d762..18bd36eb28c85c1
Roller-URL: https://ci.chromium.org/b/8741604852587470753
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: Ie1629f71aac7e2b07d4b7d1b06c842114d362918
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/examples/+/225633
Lint: Lint 🤖 <android-build-ayeaye@system.gserviceaccount.com>
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 6afbf6d..18bd36e 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 6afbf6deaa1d7623df64ae5338b7a0dd94aa6f21
+Subproject commit 18bd36eb28c85c10bf0978b5983ac1e3f16bf476