Describe the bug

The documentation at https://pipx.pypa.io/stable/docs/#pipx-upgrade says that upgrade is:

Upgrade a package in a pipx-managed Virtual Environment by running pip install --upgrade PACKAGE

pipx upgrade fails when a package is not installed, so that is not the behavior.

How to reproduce

$ pipx --version
1.4.3

$ pipx --verbose upgrade dummy_test
Package is not installed. Expected to find /Users/example/.local/pipx/venvs/dummy-test, but it does not exist.

It should have installed it if not installed, and upgraded it if installed.