DOCSP-27106 adds missing comma, fixing json snippet (#2372)

Author: jmd-mongo

source/core/index-wildcard.txt

@@ -62,7 +62,7 @@ arrays:
    {
      "product_name" : "Spy Coat",
      "product_attributes" : {
-       "material" : [ "Tweed", "Wool", "Leather" ]
+       "material" : [ "Tweed", "Wool", "Leather" ],
        "size" : {
          "length" : 72,
          "units" : "inches"