Fix/improve #2211
Remove tests for now non-existent method CI_Upload::clean_file_name()

See 7e5597782a589e4171ca08abdd9ce1a185542ff4
core comment error.

Signed-off-by: Bo-Yi Wu <appleboy.tw@gmail.com>
Merge pull request #2213 from appleboy/core

core comment error.