Fix installation of packages

Install package arcanist from Ubuntu repo and not with pip

README.md

@@ -9,7 +9,7 @@ The documentation is powered by [Sphinx](http://www.sphinx-doc.org/en/stable/) a
 Run the following command to install the needed dependencies:
 
 ```
-sudo apt install python3-pip python3-sphinx texlive-full && pip3 install sphinx_bootstrap_theme arcanist
+sudo apt install python3-pip python3-sphinx texlive-full arcanist && pip3 install sphinx_bootstrap_theme
 ```
 
 You can see the options for building the documentation by running `make help`.