Remove reference to range mode in pg_xlogdump error

pg_xlogdump doesn't have any other mode, so it's just confusing to
include this in the error message as it indicates there might be another
mode.

src/bin/pg_xlogdump/pg_xlogdump.c

@@ -949,7 +949,7 @@ main(int argc, char **argv)
 	/* we don't know what to print */
 	if (XLogRecPtrIsInvalid(private.startptr))
 	{
-		fprintf(stderr, "%s: no start log position given in range mode.\n", progname);
+		fprintf(stderr, "%s: no start log position given.\n", progname);
 		goto bad_argument;
 	}