c6f21b2ac2
After some copy-edit I made in commit 3a06a79cd137, we have a <sect2> that only contains a warning box. This doesn't look good. Rework by moving the sect2 title to be the warning's title, and put the 'id' to it as well, so that the external reference continues to work. Backpatch to 15. In branch master, I also take the opportunity to add titles to a couple of other warning boxes elsewhere in the documentation. Discussion: https://postgr.es/m/20221219164713.ccnlvtkyj6lmshqq@alvherre.pgsql