[roll] Roll fuchsia [gndoc] Update GN build arguments documentation

Roller-URL: https://ci.chromium.org/b/8835814708177189457
Cq-Cl-Tag: roller-builder:fuchsia-docs-roller
Cq-Cl-Tag: roller-bid:8835814708177189457
CQ-Do-Not-Cancel-Tryjobs: true
Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/582844
Original-Revision: 3d8d9ff2cbb92e6eca5bd2e6b930b29afc1653be
GitOrigin-RevId: bd738c96b03fc9790b7afd58866281aa2e2293ef
Change-Id: I447fedf7839b4832500cd1546833086f7bb249a1
diff --git a/stem b/stem
index 2f49463..de68090 100644
--- a/stem
+++ b/stem
@@ -10,7 +10,7 @@
              githooks=""
              remote="https://fuchsia.googlesource.com/fuchsia"
              gerrithost="https://fuchsia-review.googlesource.com"
-             revision="8a36658d2b9101f52aea20e10a002e2c78776aaa"/>
+             revision="3d8d9ff2cbb92e6eca5bd2e6b930b29afc1653be"/>
   </projects>
   <hooks>
     <hook name="install-environment"