Remove incorrect comment from GetWriteRecPtr(): the return value is always

correct, as described in comments at start of xlog.c

src/backend/access/transam/xlog.c

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.380 2010/03/10 02:04:48 itagaki Exp $
+ * $PostgreSQL: pgsql/src/backend/access/transam/xlog.c,v 1.381 2010/03/15 18:49:17 sriggs Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -6483,9 +6483,6 @@ GetInsertRecPtr(void)
 
 /*
  * GetWriteRecPtr -- Returns the current write position.
- *
- * NOTE: The value returned lags behind the real write position. But,
- * an approximation is enough for the current usage of this function.
  */
 XLogRecPtr
 GetWriteRecPtr(void)