Add note to use FQCN on Ansible versions <1.10 (ansible-collections#419)

Add note to use FQCN on Ansible versions <1.10

SUMMARY
Updates aws_rds inventory module documentation to add a note for uses of Ansible versions prior to 1.10 to use the fully qualified collection name to avoid issues with role assumption (Addresses ansible-collections#415 )
ISSUE TYPE

Docs Pull Request

COMPONENT NAME
aws_rds

Reviewed-by: Jill R <None>
Reviewed-by: None <None>

plugins/inventory/aws_rds.py

@@ -39,6 +39,8 @@
         iam_role_arn:
           description: The ARN of the IAM role to assume to perform the inventory lookup. You should still provide
               AWS credentials with enough privilege to perform the AssumeRole action.
+    note:
+        Ansible versions prior to 2.10 should use the fully qualified plugin name 'amazon.aws.aws_rds'.
     extends_documentation_fragment:
     - inventory_cache
     - constructed