luci-app-statistics: remove rrd path triple escape

Fixes rendering errors when RRD file names contain IPv6 addresses and the
colon (":") characters are triple escaped.

Adapts the Lua-specific fix in #4340 to Javascript.

Signed-off-by: Philip L. McMahon <philip.l.mcmahon@gmail.com>

applications/luci-app-statistics/htdocs/luci-static/resources/statistics/rrdtool.js

@@ -376,7 +376,7 @@ return baseclass.extend({
 
 		function __def(source) {
 			var inst = source.sname,
-			    rrd  = source.rrd.replace(/[\\:]/g, '\\$&'),
+			    rrd  = source.rrd,
 			    ds   = source.ds || 'value';
 
 			_args.push(