fix(service): say why the service account stays, truthfully for Rust too

`uninstall --game rust --server-id beta` printed "left the runicgateway
account alone — this installer did not create it" on a host where this
installer had created it, for alpha. A Rust instance's service never owns
the shared account (the last instance's removal decides), so the reason
now reads "it is not this service's to remove" — true for both games.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01E14m6SuuY6i1vASFeGDBeY

src/service.rs

@@ -973,8 +973,11 @@ fn remove_platform(record: &ServiceRecord) -> Removal {
             )),
         }
     } else if let Some(user) = record.user.as_deref() {
+        // Not "this installer did not create it": a Rust instance's service never owns the account
+        // even when this installer made it, because every instance shares it — the last instance's
+        // removal decides (`rustgame::uninstall`). Said that way, the line is true for both games.
         out.done.push(format!(
-            "left the {user} account alone — this installer did not create it"
+            "left the {user} account alone — it is not this service's to remove"
         ));
     }
     out