js/search/engine.js: removed ekn:// custom implementation
js/search/engine.js: removed ekn:// custom implementation

Replaced ekn:// custom implementation with system wide EknVfs support.

https://phabricator.endlessm.com/T14073

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