Further improvements to e2ee logging (#2900)

A followup to #2884. In particular, it is not always the case that the
`sender_key` in a `m.room_key_withheld` message is the sender of that message.

src/crypto/index.ts

@@ -3269,9 +3269,9 @@ export class Crypto extends TypedEventEmitter<CryptoEvent, CryptoEventHandlerMap
         }
 
         logger.info(
-            `Got room key withheld event from ${event.getSender()} (${content.sender_key}) `
-            + `for ${content.algorithm}/${content.room_id}/${content.session_id} `
-            + `with reason ${content.code} (${content.reason})`,
+            `Got room key withheld event from ${event.getSender()} `
+            + `for ${content.algorithm} session ${content.sender_key}|${content.session_id} `
+            + `in room ${content.room_id} with code ${content.code} (${content.reason})`,
         );
 
         const alg = this.getRoomDecryptor(content.room_id, content.algorithm);