[roll] Roll fuchsia [gcs][oauth2] use query_pairs_mut

Followup for
https://fuchsia-review.git.corp.google.com/c/fuchsia/+/749254/5/src/lib/gcs/src/auth/pkce.rs#172
to use query_pairs_mut rather than formatting a string.

Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/760842
Original-Revision: 0466940ab3b24efbee5a1b94a6890e302315b175
GitOrigin-RevId: e0abdc2f1665654120803d00836a2842142d1941
Change-Id: I723ab9a521118ca8d81386e9cbb3b015fec14b03
diff --git a/stem b/stem
index 6d12e1b..d49e2db 100644
--- a/stem
+++ b/stem
@@ -11,7 +11,7 @@
              githooks="integration/git-hooks"
              remote="https://fuchsia.googlesource.com/fuchsia"
              gerrithost="https://fuchsia-review.googlesource.com"
-             revision="e6a69d75a987640f1630689ffe837e64311e7a3e"/>
+             revision="0466940ab3b24efbee5a1b94a6890e302315b175"/>
   </projects>
   <hooks>
     <hook name="install-environment"