fix a small typo in development.environment.rst

virutalenv ==> virtualenv

Change-Id: If090ab7b92230fba15d7be98a84b51cce507bedd
Closes-bug: 1358531

doc/source/devref/development.environment.rst

@@ -123,7 +123,7 @@ You can manually install the virtual environment instead of having
 This will install all of the Python packages listed in the
 ``requirements.txt`` file into your virtualenv. There will also be some
 additional packages (pip, setuptools) that are installed
-by the ``tools/install_venv.py`` file into the virutalenv.
+by the ``tools/install_venv.py`` file into the virtualenv.
 
 If all goes well, you should get a message something like this::