deploy: move the swarm collector toggle

The one move where the suffix grep is the wrong instrument. There are two
otel options a word apart — `swarm.otel.enable` (one per swarm) and
`otel.enable` (one per hive, every hive runs it) — so `\.otel\.enable`
matches twenty-five references of which most must not change. The module
already carries a comment warning about exactly this, on a line that
names `swarm.otel` in full rather than through a binding.

Triaged by hand and confirmed the other way round: after the move, a grep
for the per-hive option still finds it in the files that should keep it.

Also worth recording what the alias sweep cannot do. `swarm.nix` reads
this as `swarmCfg.otel.enable`, where `swarmCfg = cfg.swarm` and `cfg =
config.services.hyperhive` — an alias bound to an alias, two hops from
the option path. No syntactic sweep resolves that chain, which is why the
module system's own evaluation is the only complete check here and the
static sweeps are a way to narrow the work, not to finish it.

nix/host-modules/swarm.nix

@@ -60,7 +60,7 @@ let
   # failed every POST and dropped the samples.
   ++ lib.optional deployCfg.grafana swarmCfg.grafana.domain
   ++ lib.optional deployCfg.victoriametrics swarmCfg.victoriametrics.domain
-  ++ lib.optional swarmCfg.otel.enable swarmCfg.otel.domain
+  ++ lib.optional deployCfg.otel swarmCfg.otel.domain
   # VictoriaLogs' vhost is new (was previously unpublished entirely — see
   # swarm-victorialogs.nix's file-top comment) and needs the same
   # membership every gateway-published swarm service needs: absent from