Remove extra increment of plpgsql's statement counter for FOR loops.
This left gaps in the internal statement numbering, which is not
terribly harmful (else we'd have noticed sooner), but it's not
great either.
Oversight in
bbd5c207b; backpatch to v12 where that came in.
Pavel Stehule
Discussion: https://postgr.es/m/CAFj8pRDXyQaJmpotNTQVc-t-WxdWZC35V2PnmwOaV1-taidFWA@mail.gmail.com