fix prefix sub command and add clearing guild prefixes

fix some issues with hover events in prefixes

build.gradle.kts

@@ -1,3 +1,4 @@
+import java.nio.charset.StandardCharsets
 plugins {
     java
     `maven-publish`
@@ -49,4 +50,8 @@ tasks {
     javadoc {
         options.memberLevel = JavadocMemberLevel.PRIVATE
     }
+    compileJava {
+        options.encoding = StandardCharsets.UTF_8.name()
+        options.release.set(17)
+    }
 }