remove duplicative prometheus function

public/app/plugins/datasource/prometheus/mode-prometheus.js

@@ -111,11 +111,6 @@ var keyWordsCompletions = prometheusKeyWords.map(function(word) {
 });
 
 var prometheusFunctions = [
-  {
-    name: 'abs()', value: 'abs',
-    def: 'abs(v instant-vector)',
-    docText: 'Returns the input vector with all sample values converted to their absolute value.'
-  },
   {
     name: 'abs()', value: 'abs',
     def: 'abs(v instant-vector)',