Change "iff" -> "if" in example docstrings.

pep-0484.txt

@@ -1916,7 +1916,7 @@ Example::
 
   def send_email(address, sender, cc, bcc, subject, body):
       # type: (...) -> bool
-      """Send an email message.  Return True iff successful."""
+      """Send an email message.  Return True if successful."""
       <code>
 
 Sometimes you have a long list of parameters and specifying their
@@ -1935,7 +1935,7 @@ last argument (if any) should precede the close parenthesis.  Example::
                  body=None    # type: List[str]
                  ):
       # type: (...) -> bool
-      """Send an email message.  Return True iff successful."""
+      """Send an email message.  Return True if successful."""
       <code>
 
 Notes: