Fix "mongodb" export format example

Author: jakeboone02

docs/api/export.mdx

@@ -165,7 +165,7 @@ formatQuery(query, "mongodb");
 Output:
 
 ```ts
-`{$and:[{firstName:{$eq:"Steve"}},{lastName:{$eq:"Vai"}}]}`;
+`{"$and":[{"firstName":{"$eq":"Steve"}},{"lastName":{"$eq":"Vai"}}]}`;
 ```
 
 ## Configuration