Remove mxdev from installation instruction.

Author: ksuess

docs/install/install-from-packages.md

@@ -49,7 +49,7 @@ You may host multiple Plone sites on the same server.
 Installing Python is beyond the scope of this documentation.
 However, it is recommended to use a Python version manager, [`pyenv`](https://github.com/pyenv/pyenv) that allows you to install multiple versions of Python on your development environment without destroying your system's Python.
 
-Install or upgrade {term}`Cookiecutter` and {term}`mxdev` in your user's Python:
+Install or upgrade {term}`Cookiecutter` in your user's Python:
 
 ```shell
 pip install --user --upgrade cookiecutter