You can uninstall or removes an installed ca-certificates-mono package itself from Ubuntu 16.10 (Yakkety Yak) through the terminal,
$ sudo apt-get remove ca-certificates-mono
If you would like to remove ca-certificates-mono and it's dependent packages which are no longer needed from Ubuntu,
$ sudo apt-get remove --auto-remove ca-certificates-mono
If you use with purge options to ca-certificates-mono package all the configuration and dependent packages will be removed.
$ sudo apt-get purge ca-certificates-mono
If you use purge options along with auto remove, will be removed everything regarding the package, It's really useful when you want to reinstall again.
$ sudo apt-get purge --auto-remove ca-certificates-mono