Doc: fix bogus example about ambiguous timestamps.
I had a brain fade in commit
d32899157, and used 2:30AM as the
example timestamp for both spring-forward and fall-back cases.
But it's not actually ambiguous at all in the fall-back case,
because that transition is from 2AM to 1AM under USA rules.
Fix the example to use 1:30AM, which *is* ambiguous.
Noted while answering a question from Aleksander Alekseev.
Back-patch to all supported branches.
Discussion: https://postgr.es/m/
2191355.
1641828552@sss.pgh.pa.us