Remove to_json

We no longer need to turn the string into json. Currently that action
is causing chars like quotes and newlines to show up.

.github/workflows/scripts/slack_notifications/cve_notifier.rb

@@ -29,7 +29,7 @@ def self.feed
   end
 
   def self.cve_message(title, url)
-    ":rotating_light: #{title}\n<#{url}|More info here>".to_json
+    ":rotating_light: #{title}\n<#{url}|More info here>"
   end
 end