Clarify "getting started" docs (#963)

* Clarify "getting started" docs

This makes it clearer that you don't need to use both virtualenv and venv at the same time

* Update doc/source/start.rst

---------

Co-authored-by: Luke Hinds <[email protected]>
Co-authored-by: Eric Brown <[email protected]>

Author: 3 people

doc/source/start.rst

@@ -6,17 +6,17 @@ Installation
 
 Bandit is distributed on PyPI. The best way to install it is with pip.
 
-Create a virtual environment (optional):
+Create a virtual environment and activate it using `virtualenv` (optional):
 
 .. code-block:: console
 
     virtualenv bandit-env
-    python3 -m venv bandit-env
-
-And activate it:
+    source bandit-env/bin/activate
+Alternatively, use `venv` instead of `virtualenv` (optional):
 
 .. code-block:: console
 
+    python3 -m venv bandit-env
     source bandit-env/bin/activate
 
 Install Bandit: