deploy: fix a reference the option-path sweep could not see

`ssoLocal` in the grafana module read `cfg.enable`, where `cfg` is the
local binding for `services.hyperhive.swarm.grafana` — the option set the
previous commit removed `enable` from. Evaluation fails on the missing
attribute.

The sweep that missed it looked for the option *path*
(`grafana.enable`). This reference is spelled through a `let` alias, so
no grep for the path can find it, and a parse check cannot either: it is
syntactically valid and only wrong once the module system resolves the
attribute.

The check that does find it: for each file, extract the local bindings
that point at the option set being changed, then grep for
`<alias>.<removed-attr>`. Run against this tree it reports nothing for
grafana and sixteen references for authelia, which is the next module to
move.

nix/host-modules/swarm-grafana.nix

@@ -77,7 +77,7 @@ let
   # The all-local case: this host runs BOTH Grafana and the swarm's authelia,
   # so the minted secret can be moved without an operator. Same split the
   # forge and matrix modules document.
-  ssoLocal = cfg.enable && autheliaCfg.enable;
+  ssoLocal = deployCfg.grafana && autheliaCfg.enable;
   autheliaUrl = toString autheliaCfg.url;
 
   # Where the plaintext lands inside the container. Under /var/lib rather