To uninstall talk just follow these instructions.
sudo apt-get remove talk
This will remove just the talk package itself.
sudo apt-get remove --auto-remove talk
This will remove the talk package and any other dependant packages which are no longer needed.
If you also want to delete your local/config files for talk then this will work.
sudo apt-get purge talk
Or similarly, like this talk
sudo apt-get purge --auto-remove talk
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