chore: fix a typo (#16104)

dolphinscheduler-api/src/main/java/org/apache/dolphinscheduler/api/exceptions/ApiExceptionHandler.java

@@ -44,7 +44,7 @@ public class ApiExceptionHandler {
     @ExceptionHandler(Throwable.class)
     public Result<Object> exceptionHandler(Throwable e, HandlerMethod hm) {
         ApiException ce = hm.getMethodAnnotation(ApiException.class);
-        log.error("Meet en unknown exception: ", e);
+        log.error("Meet an unknown exception: ", e);
         if (ce == null) {
             return Result.errorWithArgs(Status.INTERNAL_SERVER_ERROR_ARGS, e.getMessage());
         }