Flag slow test as a smoke_test

[mark-dce]

This test doesn't test any code that isn't tested elsewhere,
it just tests it more times by runing the full production config file
that sets up 21 admin sets - i.e. it runs the same tests 21 times.

While it's somewhat useful to know that all currently configured
admin sets in config/emory/admin_sets.yml are setup correctly, that
can be manually verified in the dashboard on the page at
https://etd.library.emory.edu/schools

Long term, this check probably belongs in some kind of deployment check
rather than the main test suite.

[coveralls]

Coverage remained the same at 92.119% when pulling b0b7684 on slow_test into b85fa17 on main.

[mark-dce]

I'm merging this since coveralls reports no change in coverage and it speeds up the test suite.