migrate dprecated $.isArray to Array.isArray

`$.isArray` is deprecated in jQuery 3.2, so Array.isArray should be the way to go.

jquery/jquery#2961
https://blog.jquery.com/2017/03/16/jquery-3-2-0-is-out/

Author: erotte

src/jquery.autocomplete.js

@@ -138,7 +138,7 @@
         if (!currentValue) {
             return suggestion.value;
         }
-        
+
         var pattern = '(' + utils.escapeRegExChars(currentValue) + ')';
 
         return suggestion.value
@@ -237,7 +237,7 @@
                 that.hide();
             }, 200);
         },
-        
+
         abortAjax: function () {
             var that = this;
             if (that.currentRequest) {
@@ -252,7 +252,7 @@
 
             this.options = $.extend({}, options, suppliedOptions);
 
-            that.isLocal = $.isArray(options.lookup);
+            that.isLocal = Array.isArray(options.lookup);
 
             if (that.isLocal) {
                 options.lookup = that.verifySuggestionsFormat(options.lookup);
@@ -558,7 +558,7 @@
                 response = that.cachedResponse[cacheKey];
             }
 
-            if (response && $.isArray(response.suggestions)) {
+            if (response && Array.isArray(response.suggestions)) {
                 that.suggestions = response.suggestions;
                 that.suggest();
                 options.onSearchComplete.call(that.element, q, response.suggestions);
@@ -704,7 +704,7 @@
             noSuggestionsContainer.detach();
 
             // clean suggestions if any
-            container.empty(); 
+            container.empty();
             container.append(noSuggestionsContainer);
 
             if ($.isFunction(beforeRender)) {