Fix unused import

Author: rwinch

Diff for: web/src/main/java/org/springframework/security/web/authentication/HttpMessageConverterAuthenticationSuccessHandler.java

@@ -18,7 +18,6 @@
 
 import java.io.IOException;
 
-import com.fasterxml.jackson.databind.json.JsonMapper;
 import jakarta.servlet.ServletException;
 import jakarta.servlet.http.HttpServletRequest;
 import jakarta.servlet.http.HttpServletResponse;