Update changes.rst for MR !299 (diadct with xios)

source/changes.rst

@@ -56,6 +56,7 @@ List of the main bugfixes in the new 4.2.1 release - May 2023
 - Some dia_ar5_hst outputs were wrong (:mergereq:`140`)
 - The qsr3d diagnostic could not be output (:mergereq:`296`)
 - Some dia_ar5 diagnostics could not be output, and some diagnostics gave different results with tiling (:mergereq:`301`)
+- diadct mfo/sfo/hfo transports through sections are now handled by XIOS (:mergereq:`299`)
 
 ###################
 Changes since 4.0.7