Update 3.12.8.md

Fix typo

(cherry picked from commit d1ee7d8)

Author: johanrhodin

release-notes/3.12.8.md

@@ -35,7 +35,7 @@ Release notes can be found on GitHub at [rabbitmq-server/release-notes](https://
 #### Enhancements
 
  * `raft.segment_max_entries` is now validated to prevent the value from overflowing its 16-bit segment file field.
-   Maximum supported value is now ``65535.
+   Maximum supported value is now `65535`.
 
    GitHub issue: [#9733](https://github.com/rabbitmq/rabbitmq-server/issues/9733)