Editorial: Correct typo (#412)

Author: jugglinmike

index.bs

@@ -995,7 +995,7 @@ the listener if it wants.
 
 To <dfn>close the WebSocket connections</dfn> given |session|:
 
-1. For each |connection| in |session|'s[=session WebSocket
+1. For each |connection| in |session|'s [=session WebSocket
    connections=]:
 
   1. [=Start the WebSocket closing handshake=] with |connection|.