[roll] Roll fuchsia [ffx] Cleanup compatibility code for architecture

CL 674057 changed the host.architecture field to use an enumeration,
which modified its serialized form. To account for this, we introduced
compatibility code to the tool to handle both serialized forms, to make
sure we didn't break running emulators that still had the old serialized
data.

It's been about 3 months since that CL landed, so this CL removes the
compatibility code, such that we now only accept the new form based on
the enumeration type. It's expected that any emulators that were running
when that CL landed have been torn down, and the SDKs thah held the old
version of the tool have been upgraded by now, so no more instances of
the old serialized data should still be around.

Original-Bug: 99291
Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/701543
Original-Revision: 0e13a59e12a79550f065deb34c86fe82aefe5b94
GitOrigin-RevId: d0a6008c047403b0376dec53f18f20b1fbf495f7
Change-Id: I26ff6e9e18d94cf464c134fc9dd833aa91fd4d56
diff --git a/stem b/stem
index 77cebc8..46d1cd7 100644
--- a/stem
+++ b/stem
@@ -10,7 +10,7 @@
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              remote="https://fuchsia.googlesource.com/fuchsia"
              gerrithost="https://fuchsia-review.googlesource.com"
-             revision="dae6d992d7e28daf9bb6994082f6f72688990b3c"/>
+             revision="0e13a59e12a79550f065deb34c86fe82aefe5b94"/>
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