Checkstyle fixes

Signed-off-by: Raihan M <muhamedraihan@gmail.com>

Author: raihio

protocol/src/main/java/org/fidoalliance/fdo/protocol/Mapper.java

@@ -135,11 +135,13 @@ public byte[] writeAsCborByteString(Object value) throws IOException {
     return cborMapper.writeValueAsBytes(writeValue(value));
   }
 
-    /**
-     * @return A CBOR Null value.
-     */
+  /**
+   * Returns a CBOR Null value.
+   *
+   * @return A CBOR Null value.
+   */
   public byte[] cborNull() {
-      return new byte[]{(byte) 0xf6};
+    return new byte[]{(byte) 0xf6};
   }
 
   /**