tests: improve Webperimental loads check.
tests: improve Webperimental loads check.

Test that the webperimental ruleset loads rather than that the current
ruleset printed a word webperimental also prints.

andreasrosdal/freeciv-web,andreasrosdal/freeciv-web,andreasrosdal/freeciv-web,andreasrosdal/freeciv-web,andreasrosdal/freeciv-web