ci: fix release notes compare link (#8581)

Co-authored-by: Mathias Fredriksson <mafredri@gmail.com>

scripts/release/generate_release_notes.sh

@@ -54,6 +54,9 @@ fi
 if [[ -z $new_version ]]; then
 	error "No new version specified"
 fi
+if [[ $new_version != v* ]]; then
+	error "New version must start with a v"
+fi
 if [[ -z $ref ]]; then
 	error "No ref specified"
 fi