Fix formatting issues in SockJsFrame by organizing imports

Signed-off-by: KNU-K <[email protected]>

Author: polyglot-k

spring-websocket/src/main/java/org/springframework/web/socket/sockjs/frame/SockJsFrame.java

@@ -16,10 +16,11 @@
 
 package org.springframework.web.socket.sockjs.frame;
 
-
 import java.nio.charset.Charset;
 import java.nio.charset.StandardCharsets;
+
 import org.jspecify.annotations.Nullable;
+
 import org.springframework.util.Assert;
 
 /**