message: doc: Add release notes for 15629
diff: @@ -73,9 +73,14 @@ Example item
  Low-level changes
  =================
  -Example item
  +Configuration
  ------------
  +* An error is issued where previously a warning was issued when a setting in
  + the config file was specified in the default section, but not overriden for
  + the selected network. This change takes only effect if the selected network
  + is not mainnet.
  +
  Credits
  =======
  