$ sudo apt-get remove elpa-flx 

Uninstall elpa-flx including dependent package

If you would like to remove elpa-flx and it's dependent packages which are no longer needed from Ubuntu,

$ sudo apt-get remove --auto-remove elpa-flx 

Use Purging elpa-flx

If you use with purge options to elpa-flx package all the configuration and dependent packages will be removed.

$ sudo apt-get purge elpa-flx 

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 elpa-flx 

See Also,