Update comment and task title.

playbooks/roles/edxapp/tasks/main.yml

@@ -82,8 +82,8 @@
   - install
 
 
-# Install the python post requirements into {{ venv_dir }}
-- name : install python post-requirements
+# Install the python pre requirements into {{ venv_dir }}
+- name : install python pre-requirements
   pip: requirements="{{pre_requirements_file}}" virtualenv="{{venv_dir}}" state=present
   tags:
   - lms