DOCS-15915 backticks (#2664)

Author: Dave Cuthbert

source/release-notes/6.0.txt

@@ -42,7 +42,7 @@ Issues Fixed:
 - :issue:`SERVER-70395` Slot-Based Engine too aggressively uses disk for
   $group and is slow
 - :issue:`SERVER-73232` Change the default log-verbosity for
-  `_killOperations`
+  ``_killOperations``
 
 - `All JIRA issues closed in 6.0.5
   <https://jira.mongodb.org/issues/?jql=project%20in%20(SERVER%2CTOOLS%2CWT)%20AND%20resolution%3D%27Fixed%27%20and%20fixversion%3D%276.0.5%27>`_