Use default btn styling for Housekeeping button on projects settings page

Changes the Housekeeping button styling on the project settings page from ```btn-save``` to ```btn-default```

**BEFORE:** ![Screen_Shot_2016-12-06_at_12_51_42_PM](/uploads/1b1c8a26eead025062e2c98d9d0f4286/Screen_Shot_2016-12-06_at_12_51_42_PM.png)

**AFTER:** ![Screen_Shot_2016-12-06_at_12_51_57_PM](/uploads/9e7937af4a058fa1aa8b45653dbad3ee/Screen_Shot_2016-12-06_at_12_51_57_PM.png)

Closes #25324 
cc: @awhildy

See merge request !7959