[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/8825766072635299185
Cq-Cl-Tag: roller-builder:pigweed-experimental-roller
Cq-Cl-Tag: roller-bid:8825766072635299185
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: Ifea28cca7ef17867015bd3555d46a4cbea911f60
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/experimental/+/77121
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