You're reading the documentation for a version of ROS 2 that has reached its EOL (end-of-life), and is no longer officially supported. If you want up-to-date information, please have a look at Galactic.
Building ROS 2 on Fedora Linux
How to setup the development environment?
First install a bunch of dependencies:
$ sudo dnf install cppcheck cmake libXaw-devel opencv-devel poco-devel poco-foundation python3-empy python3-devel python3-nose python3-pip python3-pyparsing python3-pytest python3-pytest-cov python3-pytest-runner python3-setuptools python3-yaml tinyxml-devel eigen3-devel python3-pydocstyle python3-pyflakes python3-coverage python3-mock python3-pep8 uncrustify python3-argcomplete python3-flake8 python3-flake8-import-order asio-devel tinyxml2-devel libyaml-devel python3-lxml
Then install vcstool from pip:
$ pip3 install vcstool
With this done, you can follow the rest of the instructions to fetch and build ROS 2.