[roll] Roll fuchsia Revert "Reland "[overnet] Remove legacy Overnet""

This reverts commit dee883548ea7ee9a6e41797bcf0c0d815e148d9b.

Reason for revert: Seems to have broken downstream google3 users

Original change's description:
> Reland "[overnet] Remove legacy Overnet"
>
> This is a reland of commit bfe7734737efc62a49b3482fce84b9e3a6352c2a
>
> Original change's description:
> > [overnet] Remove legacy Overnet
> >
> > Feels like this should have a longer description but that's pretty much
> > it. We're removing legacy overnet and all the code that supports it.
> >
> > Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/864287
>
> Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/909255

No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/912595
Original-Revision: 21091ed9cf1275da35e0def7acd9b98a74ca9a9b
GitOrigin-RevId: 69c2043f623b33487756c7411b8ede74719a75f7
Change-Id: I137693b628be3fb401c7e1ecd4bdd54e713a238b
diff --git a/stem b/stem
index 61937c0..68e5f37 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="ec1e996001d76e0608c4b018e968b7768e982840"/>
+             revision="21091ed9cf1275da35e0def7acd9b98a74ca9a9b"/>
   </projects>
   <hooks>
     <hook name="install-environment"