dialect/sql: make sql.In() with empty args fallback to False() (#2735)

* dialect/sql/builder: make sql.In() with empty args fallback to False()

* fix indent

* added comment

* remove the equilvalent logic in the codegen side

* comment fix, run go generate

entc/gen/template/dialect/sql/predicate.tmpl

@@ -18,12 +18,6 @@ in the LICENSE file in the root directory of this source tree.
 	{{- $storage := $.Scope.Storage -}}
 	func(s *sql.Selector) {
 		{{- if $op.Variadic }}
-			// if not arguments were provided, append the FALSE constants,
-			// since we can't apply "IN ()". This will make this predicate falsy.
-			if len({{ $arg }}) == 0 {
-				s.Where(sql.False())
-				return
-			}
 			v := make([]interface{}, len({{ $arg }}))
 			for i := range v {
 				v[i] = {{ $arg }}[i]