Doc: Unify spam to junk.

Documentation/UseCase.rst

@@ -119,7 +119,7 @@ QFQ content record::
     form={{SELECT IF('{{action:SE}}' = '','registration','') }}
 
     20.sql = SELECT "<p>Thank you for your registration.</p><p>An email with further instructions has been sent to you.</p>"
-                    , "<p>You should receive the mail during the next 5 minutes. If not, please check your SPAM folder.</p>"
+                    , "<p>You should receive the mail during the next 5 minutes. If not, please check your JUNK folder.</p>"
 
                 FROM (SELECT '') AS fake
                 WHERE '{{action:SE}}' = 'thanksRegistration'
@@ -216,7 +216,7 @@ QFQ content record::
       head = <div class="alert alert-success">
                <p>Thank you.</p>
                <p>If the email address is known in our database, we sent a password reset link to it.</p>
-               <p>The mail should be received during the next minutes. If not, please check you junk folder.</p>
+               <p>The mail should be received during the next minutes. If not, please check you JUNK folder.</p>
                <p>To set a new password, please click on the link provided in the email.</p>
              </div>
     }