doc: Add release notes for -printtoconsole and -debuglogfile changes

This adds release notes relevant to the changes in #13004 and documented in command line help in #13614

Author: satwo

doc/release-notes.md

@@ -131,6 +131,11 @@ Low-level RPC changes
 
 - The log timestamp format is now ISO 8601 (e.g. "2018-02-28T12:34:56Z").
 
+- When running bitcoind with `-debug` but without `-daemon`, logging to stdout
+  is now the default behavior. Setting `-printtoconsole=1` no longer implicitly
+  disables logging to debug.log. Instead, logging to file can be explicitly disabled
+  by setting `-debuglogfile=0`.
+
 Miner block size removed
 ------------------------