Simplify constructor

mirai-core/src/commonMain/kotlin/net.mamoe.mirai/contact/MessageTooLargeException.kt → mirai-core/src/commonMain/kotlin/net.mamoe.mirai/contact/exceptions.kt

@@ -40,10 +40,7 @@ class MessageTooLargeException(
  */
 @SinceMirai("0.33.0")
 class BotIsBeingMutedException(
-    val target: Group,
-    /**
-     * 被禁言剩余时间
-     * @see Group.botMuteRemaining
-     */
+    val target: Group
+) : RuntimeException("bot is being muted, remaining ${target.botMuteRemaining} seconds")
+
+val BotIsBeingMutedException.botMuteRemaining: Int get() = target.botMuteRemaining
\ No newline at end of file
-    val remainingMillis: Int
-) : RuntimeException()
\ No newline at end of file