Fix thinko in join removal.
In commit
9df8f903e I (tgl) switched join_is_removable() from
using the min relid sets of the join under consideration to
using its full syntactic relid sets. This was a mistake,
as it allowed join removal in cases where a reference to the
join output would survive in some syntactically-lower join
condition. Revert to the former coding.
Richard Guo
Discussion: https://postgr.es/m/CAMbWs4-EU9uBGSP7G-iTwLBhRQ=rnZKvFDhD+n+xhajokyPCKg@mail.gmail.com