[roll third_party/pigweed] docs: New contributors should sign in to Gerrit

If this step is skipped, then trying to push a CL will yield a
PERMISSION_DENIED_BY_GERRIT_ACL error saying that "\'git push\'
requires a Gerrit user account".

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/76922

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 79f3767c95beb36..4b7b09e44f828a2
Roller-URL: https://ci.chromium.org/b/8825766072706752705
Cq-Cl-Tag: roller-builder:pigweed-sample-project-roller
Cq-Cl-Tag: roller-bid:8825766072706752705
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: Iedd4bd185ecbba3365dac46de4f3e35169e5be72
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/sample_project/+/77120
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 79f3767..4b7b09e 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 79f3767c95beb362d51c2a7b589b926347e7dc28
+Subproject commit 4b7b09e44f828a2a6b105960835b6439fcfaf829