Fix assertion in plugin page test
Fix assertion in plugin page test

The previous assertion was not correct, so I'm not sure how it was
actually working.  The new assertion says: once disabling the only
enabled plugin, there should be zero plugins enabled.

girder/girder,jbeezley/girder,kotfic/girder,jbeezley/girder,RafaelPalomar/girder,RafaelPalomar/girder,girder/girder,kotfic/girder,girder/girder,jbeezley/girder,RafaelPalomar/girder,manthey/girder,RafaelPalomar/girder,Kitware/girder,RafaelPalomar/girder,manthey/girder,manthey/girder,Kitware/girder,manthey/girder,girder/girder,kotfic/girder,kotfic/girder,kotfic/girder,jbeezley/girder,Kitware/girder,Kitware/girder