Update migration guide

Author: jacekwegr

doc/migrations/6.2.1_6.3.0.md

@@ -63,7 +63,7 @@ The simplest configuration to have it available on port `9090` on the `/metrcis`
     ```toml
     [[listen.http]]
       port = 9090
-      
+
       [[listen.http.handlers.mongoose_prometheus_handler]]
         host = "_"
         path = "/metrics"
@@ -122,5 +122,3 @@ To configure CockroachDB, update the connection settings in your configuration f
 ```
 
 Refer to the [Outgoing connections configuration doc](../configuration/outgoing-connections.md) for more information.
-
-The migration script for CockroachDB , `cockroachdb.sql` is located in the [`priv/migrations`](https://github.com/esl/MongooseIM/tree/master/priv/migrations) directory.