roll: third_party/pigweed: docs: Fix shortlink URL

It should have linked directly to the tutorial.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/221751
Lint: Lint 🤖 <android-build-ayeaye@system.gserviceaccount.com>

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 45fd25bd3ef49ea..73ef002b92f1710
Roller-URL: https://ci.chromium.org/b/8742755260568121969
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: Ie0910d5b276cb7e6b526b1e1c22e406ce304cac7
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/221851
Commit-Queue: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
Lint: Lint 🤖 <android-build-ayeaye@system.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 45fd25b..73ef002 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 45fd25bd3ef49ea9ec3cb2fc1a0f8caba7a6459a
+Subproject commit 73ef002b92f1710537635fdb38c59dc1073d025e