Please be aware that you have absolutely no benefit / advantage in doing so.
Klipper use a virtual environment that is created with a defined Python version and needs to be recreated if changing the Python version.
You have two options:
- Reinstall using the Python 3 option of GitHub - th33xitus/kiauh: Klipper Installation And Update Helper if you do not feel comfortable with working in a shell
- Do it manually after removing Python 2
sudo service klipper stop
# remove current klippy-env environment
cd ~
rm -rf klippy-env
# create new venv
virtualenv -p python3 klippy-env
#install new Klipper venv
cd ~/klippy-env
bin/pip install -r ../klipper/scripts/klippy-requirements.txt