Docs: remove references to "approved sending domains".

Mandrill dropped the requirement for pre-approving the from_email address a while back.

README.rst

@@ -107,9 +107,6 @@ Djrill 1-2-3
         # Send it:
         msg.send()
 
-   (Be sure to use a ``from_email`` that's in one of your Mandrill approved sending
-   domains, or the message won't get sent.)
-
 .. END quickstart
 
 

docs/usage/sending_mail.rst

@@ -25,10 +25,6 @@ Some notes and limitations:
     ("email\@example.com") or can include a display name
     ("Real Name <email\@example.com>").
 
-**From Address**
-    The ``from_email`` must be in one of the approved sending
-    domains in your Mandrill account, or Mandrill will refuse to send the message.
-
 **CC Recipients**
     Djrill treats all "cc" recipients as if they were
     additional "to" addresses. (Mandrill does not distinguish "cc" from "to".)