[improve][broker] Unreasonable AuthenticationException reference (apache#18502)

(cherry picked from commit e5e5852)

Author: zzccctv

pulsar-broker-common/src/main/java/org/apache/pulsar/broker/authentication/AuthenticationService.java

@@ -87,7 +87,6 @@ public AuthenticationService(ServiceConfiguration conf) throws PulsarServerExcep
 
     public String authenticateHttpRequest(HttpServletRequest request, AuthenticationDataSource authData)
             throws AuthenticationException {
-        AuthenticationException authenticationException = null;
         String authMethodName = request.getHeader(AuthenticationFilter.PULSAR_AUTH_METHOD_NAME);
 
         if (authMethodName != null) {
@@ -108,8 +107,6 @@ public String authenticateHttpRequest(HttpServletRequest request, Authentication
                     LOG.debug("Authentication failed for provider " + providerToUse.getAuthMethodName() + " : "
                             + e.getMessage(), e);
                 }
-                // Store the exception so we can throw it later instead of a generic one
-                authenticationException = e;
                 throw e;
             }
         } else {
@@ -133,11 +130,7 @@ public String authenticateHttpRequest(HttpServletRequest request, Authentication
                 return anonymousUserRole;
             }
             // If at least a provider was configured, then the authentication needs to be provider
-            if (authenticationException != null) {
-                throw authenticationException;
-            } else {
-                throw new AuthenticationException("Authentication required");
-            }
+            throw new AuthenticationException("Authentication required");
         } else {
             // No authentication required
             return "<none>";