doc: correct buffer.slice arg syntax

sam-github · Fishrock123 · commit 302d59dce833 · 2015-09-16T16:07:58.000-04:00
PR-URL: #2903 Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
diff --git a/doc/api/buffer.markdown b/doc/api/buffer.markdown
@@ -364,7 +364,7 @@ region in the same buffer
     // efghijghijklmnopqrstuvwxyz
 
 
-### buf.slice([start][, end])
+### buf.slice([start[, end]])
 
 * `start` Number, Optional, Default: 0
 * `end` Number, Optional, Default: `buffer.length`
