Enhancement/remove version check add get version

[DaveYesland]

This removes old functionality to check for updates. Pacu uses pip now with versions, this should not be used.
removes check_for_updates function in main and removes all references to it. Also removes the test for this and last_update.txt which this function used.

Created get_pacu_version function in main to return the current version of Pacu from pyproject.toml, import toml package to parse it and added pyproject.toml to the file includes for poetry.