DOCSP-34433 Add array brackets to dropIndex example (#6245)

* DOCSP-34433 add array

* DOCSP-34433 fix spacing

Author: jocelyn-mendez1

source/core/indexes/drop-index.txt

@@ -77,7 +77,7 @@ method and specify an array of index names:
 
 .. code-block:: javascript
 
-   db.<collection>.dropIndexes("<index1>", "<index2>", "<index3>")
+   db.<collection>.dropIndexes( [ "<index1>", "<index2>", "<index3>" ] )
 
 Drop All Indexes Except the ``_id`` Index
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~