pgsql: Fix obsolete mention of non-int64 support in CREATE SEQUENCE doc

Fix obsolete mention of non-int64 support in CREATE SEQUENCE documentation.

The old text explained what happened if we didn't have working int64
arithmetic.  Since that case has been explicitly rejected by configure
since 8.4.3, documenting it in the 9.x branches can only produce confusion.

Branch
------
master

Details
-------
http://git.postgresql.org/pg/commitdiff/2b475c5946bc8a9beaff3f57b45cc440a78561a1

Modified Files
--------------
doc/src/sgml/ref/create_sequence.sgml |    5 +----
1 file changed, 1 insertion(+), 4 deletions(-)