Raise interaction expiration time to 30s

src/main/java/wtf/beatrice/hidekobot/Cache.java

@@ -46,7 +46,7 @@ public class Cache
     private final static String expiryTimestampFormat = "yy/MM/dd HH:mm:ss";
 
     // note: discord sets interactions' expiry time to 15 minutes by default, so we can't go higher than that.
-    private final static long expiryTimeSeconds = 15L;
+    private final static long expiryTimeSeconds = 30L;
 
     // used to count e.g. uptime
     private static LocalDateTime startupTime = null;