grammar: removed a remnant of Slice

lib/grammar.js

@@ -178,9 +178,7 @@
         return new Accessor(new Literal('prototype'));
       }), o("SOAK_ACCESS Identifier", function() {
         return new Accessor($2, 'soak');
-      }), o("Index"), o("Slice", function() {
-        return new Slice($1);
-      })
+      }), o("Index")
     ],
     Index: [
       o("INDEX_START Expression INDEX_END", function() {

src/grammar.coffee

@@ -244,7 +244,6 @@ grammar =
     o "::",                                     -> new Accessor(new Literal('prototype'))
     o "SOAK_ACCESS Identifier",                 -> new Accessor $2, 'soak'
     o "Index"
-    o "Slice",                                  -> new Slice $1
   ]
 
   # Indexing into an object or array using bracket notation.