Update the LSN format in the comment example

Hi, all

Commit 2633dae2e487 standardized LSN formatting with zero-padding. However,
a mistake was made (by me) in the example within a comment.

This patch provides a fix for that.

diff --git a/src/include/access/xlogdefs.h b/src/include/access/xlogdefs.h
index 514f03df0b6..2397fb24115 100644
--- a/src/include/access/xlogdefs.h
+++ b/src/include/access/xlogdefs.h
@@ -38,7 +38,7 @@ typedef uint64 XLogRecPtr;
 /*
  * Handy macro for printing XLogRecPtr in conventional format, e.g.,
  *
- * printf("%X/08X", LSN_FORMAT_ARGS(lsn));
+ * printf("%X/%08X", LSN_FORMAT_ARGS(lsn));
  *
  * To avoid breaking translatable messages, we're directly applying the
  * LSN format instead of using a macro.

-- 
Best regards,
Japin Li
ChengDu WenWu Information Technology Co., LTD.