added version_added to key_passphrase

cloud/amazon/ec2_win_password.py

@@ -18,6 +18,7 @@ options:
       - path to the file containing the key pair used on the instance
     required: true
   key_passphrase:
+    version_added: "2.0"
     description:
       - The passphrase for the instance key pair. The key must use DES or 3DES encryption for this module to decrypt it. You can use openssl to convert your password protected keys if they do not use DES or 3DES. ex) openssl rsa -in current_key -out new_key -des3. 
     required: false