DOC: Fix formatting of ALTER TABLE REPLICA IDENTITY documentation

Hi Hacker,

While updating the documentation for patch [1], I noticed that the “ALTER
TABLE … REPLICA IDENTITY” section has incorrect indentation, with a closing
</para> placed in the wrong location. This made the SGML structure a bit
confusing to read.

Since the SGML in this area is already fairly dense, I think it would be
good to fix the indentation to improve readability. The attached patch does
not change any content or behavior; it only corrects the formatting.

[1]
https://postgr.es/m/CAEoWx2nJ71hy8R614HQr7vQhkBReO9AANPODPg0aSQs74eOdLQ@mail.gmail.com

Best regards,
--
Chao Li (Evan)
HighGo Software Co., Ltd.
https://www.highgo.com/