Documentation: correct command for installation of conan in Linux

In the documentation section "Building with conan" (https://eclipse.dev/openpass/content/html/installation_guide/60_conan.html#building-with-conan), the command apt install "conan>=2.2.0" to install conan did not work in Ubuntu 22.04, the system was unable to locate the package conan.

Using pip install "conan>=2.2.0" solved the issue.