Update driver-core/src/main/com/mongodb/MongoCredential.java

Co-authored-by: Valentin Kovalenko <valentin.male.kovalenko@gmail.com>

Author: katcharov

driver-core/src/main/com/mongodb/MongoCredential.java

@@ -659,7 +659,7 @@ public String toString() {
     @Evolving
     public interface OidcCallbackContext {
         /**
-         * @return Convenience method to obtain the username.
+         * @return Convenience method to obtain the {@linkplain MongoCredential#getUserName() username}.
          */
         @Nullable
         String getUserName();