Revert "GRAILS-10897: Add default grails.mime.types config in ControllerUnitTestMixin"

This reverts commit 2c60db2aebf5dfe169156c12aff0947a4cd65b61.
Revert "Fix tests after grails.mime.types config change"

This reverts commit 34db156fd98910914d84465bb2605da36c27a390.