add missing import

Author: danthe1st

src/main/java/net/discordjug/javabot/data/h2db/message_cache/MessageCache.java

@@ -38,6 +38,7 @@
 import net.dv8tion.jda.api.entities.Message.Attachment;
 import net.dv8tion.jda.api.entities.MessageEmbed;
 import net.dv8tion.jda.api.entities.User;
+import net.dv8tion.jda.api.entities.UserSnowflake;
 import net.dv8tion.jda.api.entities.channel.middleman.MessageChannel;
 import net.dv8tion.jda.api.interactions.components.buttons.Button;
 import net.dv8tion.jda.api.requests.restaction.MessageCreateAction;