pgsql: Correct docs about partitions and EXCLUDE constraints.

Correct docs about partitions and EXCLUDE constraints.

In version 17 we added support for cross-partition EXCLUDE
constraints, as long as they included all partition key columns and
compared them with equality (see 8c852ba9a4). I updated the docs for
exclusion constraints, but I missed that the docs for CREATE TABLE
still said that they were not supported. This commit fixes that.

Author: Paul A. Jungwirth <pj(at)illuminatedcomputing(dot)com>
Co-authored-by: Jeff Davis <pgsql(at)j-davis(dot)com>
Discussion: https://postgr.es/m/[email protected]
Backpatch-through: 17

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/6c29088fc6e269b7d64797bb62533b82afe03d93

Modified Files
--------------
doc/src/sgml/ref/create_table.sgml | 17 ++++++++++++-----
1 file changed, 12 insertions(+), 5 deletions(-)