ci: try to fix lack of RFC822 item support in madmail and make CI pass

some local debugging revealed madmail v2 does not support fetching RFC822 items
(gives an empty body) so try BODY.PEEK[] instead.

cmdeploy/src/cmdeploy/tests/plugin.py

@@ -211,7 +211,7 @@ class ImapConn:
         status, res = self.conn.select()
         if int(res[0]) == 0:
             raise ValueError("no messages in imap folder")
-        status, results = self.conn.fetch("1:*", "(RFC822)")
+        status, results = self.conn.fetch("1:*", "(BODY.PEEK[])")
         assert status == "OK"
         return results