Update ReleaseNotes.txt

Added ref to the email to markup

Author: filosam

ReleaseNotes.txt

@@ -3,7 +3,7 @@ RELEASE NOTES
 
 Latest version
 -------------------------
-9.6
+9.6 - Announced to MARKUP on 2024-03-21 [email] (https://lsv.uky.edu/scripts/wa.exe?A2=MARKUP;8072c553.2403&S=)
  * Release technicians: Gabriel Bodard, Martina Filosa, Nora White
 
  * Schema: aligned schema with TEI v. 4.7.0