corrected usage of ec2.py's profile option

this was never introduced into ansible-playbook though the docs
stated otherwise. We still explain how to use the env var to get the
same result.

docsite/rst/intro_dynamic_inventory.rst

@@ -111,9 +111,8 @@ If you use boto profiles to manage multiple AWS accounts, you can pass ``--profi
     aws_access_key_id = <prod access key>
     aws_secret_access_key = <prod secret key>
 
-You can then run ``ec2.py --profile prod`` to get the inventory for the prod account, or run playbooks with: ``ansible-playbook -i 'ec2.py --profile prod' myplaybook.yml``.
-
-Alternatively, use the ``AWS_PROFILE`` variable - e.g. ``AWS_PROFILE=prod ansible-playbook -i ec2.py myplaybook.yml``
+You can then run ``ec2.py --profile prod`` to get the inventory for the prod account, this option is not supported by ``anisble-playbook`` though.
+But you can use the ``AWS_PROFILE`` variable - e.g. ``AWS_PROFILE=prod ansible-playbook -i ec2.py myplaybook.yml``
 
 Since each region requires its own API call, if you are only using a small set of regions, feel free to edit ``ec2.ini`` and list only the regions you are interested in. There are other config options in ``ec2.ini`` including cache control, and destination variables.