ec2: add "IAM Role" to instance_profile_name

The AWS API and console docs are inconsistent about whether EC2 instances have IAM profiles or roles. Things which follow the API tend to use profile but the console uses “IAM Role”. This adds that term to the help text so it's searchable.

+label: docsite_pr

lib/ansible/modules/cloud/amazon/ec2.py

@@ -141,7 +141,7 @@ options:
   instance_profile_name:
     version_added: "1.3"
     description:
-      - Name of the IAM instance profile to use. Boto library must be 2.5.0+
+      - Name of the IAM instance profile (i.e. what the EC2 console refers to as an "IAM Role") to use. Boto library must be 2.5.0+
   instance_ids:
     version_added: "1.3"
     description: