entc/gen: remove unnecessary sqlgraph.To step on HasE predicates (#3144)

Predicate that checks existence-only do not need the 'other' table

examples/o2obidi/ent/user/where.go

@@ -265,7 +265,6 @@ func HasSpouse() predicate.User {
 	return predicate.User(func(s *sql.Selector) {
 		step := sqlgraph.NewStep(
 			sqlgraph.From(Table, FieldID),
-			sqlgraph.To(SpouseTable, FieldID),
 			sqlgraph.Edge(sqlgraph.O2O, false, SpouseTable, SpouseColumn),
 		)
 		sqlgraph.HasNeighbors(s, step)