Fix markdownlint errors

Author: agnetemoos

CHANGELOG.md

@@ -3,12 +3,12 @@
 All notable changes to this project will be documented in this file.
 
 ## [Unreleased]
+
 - [#313](https://github.com/os2display/display-api-service/pull/313)
   - Add BRND booking feed type
 - [#260](https://github.com/os2display/display-api-service/pull/260)
   - Changed how exceptions are handled in InstantBook.
 
-
 ## [2.5.1] - 2025-06-23
 
 - [#245](https://github.com/os2display/display-api-service/pull/245)