Without the change `tests` eval fails to discover `dashboard` as it's
used before it's definition in the same overlay.
The eval failed as:
$ nix build --no-link -f. octoprint.tests.plugins.octoprint-dashboard
error: attribute 'dashboard' missing
482| } // lib.optionalAttrs config.allowAliases {
483| octoprint-dashboard = self.dashboard;
| ^
484| }
After the change the eval succeeds as:
$ nix-instantiate -A octoprint.tests.plugins.dashboard
/nix/store/gxzicbfnpfgvs2qnpdn22aica4vlncns-python3.11-octoprint-plugin-dashboard-1.18.3.drv
d7e85937ee