ekncontent: Remove exclude parameter from clause functions
ekncontent: Remove exclude parameter from clause functions

The 'exclude' parameter is never actually used, and removing the unused
functionality will make it easier to port these functions to use
XapianQuery directly instead of string manipulation.

https://phabricator.endlessm.com/T20373

endlessm/eos-knowledge-lib,endlessm/eos-knowledge-lib,endlessm/eos-knowledge-lib,endlessm/eos-knowledge-lib