Update content/partials/types/_message.textile

Co-authored-by: Mark Hulbert <[email protected]>

Author: SimonWoolf

content/partials/types/_message.textile

@@ -69,7 +69,7 @@ blang[jsall].
   h6(#serial).
     default: serial
 
-  The message's serial (a server-assigned identifier that will be the same in all future updates of this message, and can be used to add annotations). Right now this will only be set if you enable annotations in "channel rules":/docs/channels#rules .<br>__Type: @String@__
+  A server-assigned identifier that will be the same in all future updates of this message. It  can be used to add annotations to a message. Serial will only be set if you enable annotations in "channel rules":/docs/channels#rules .<br>__Type: @String@__
 
   h6(#annotations).
     default: annotations