Prevent partial indexes on the table on the left hand side of a LEFT JOIN from being...

Prevent partial indexes on the table on the left hand side of a LEFT JOIN from being incorrectly qualified by a constraint in the ON clause of the join. This relaxes the rule introduced by the previous commit (as the partial indexes on the table on the rhs of the LEFT JOIN may now be qualified by terms within the ON clause).

FossilOrigin-Name: 1d6fb43a576d335d2717e94d28385178c23c81a1