docs: finalize R1-6 release notes for tag

Author: kgofron

RELEASE.md

@@ -12,7 +12,7 @@ The master branch (under development) is tested with Serval 4.1.1 and 3.3.2
 Driver depends on Serval versions, at this time. The current releases support Serval 4.1.1 and 3.0.0-3.3.2
 
 
-R1-6 (XXX, 2026)
+R1-6 (March 4, 2026)
 --------
 
 * **CONNECT/DISCONNECT (graceful reconnection without IOC restart)**: The driver now supports connection status monitoring and optional config refresh when SERVAL or the detector reconnects, so the IOC does not need to be restarted when the detector/emulator or SERVAL restarts.