fmt: fix fn return types list ending with comma (#14529)

vlib/v/fmt/tests/fn_types_list_ending_with_comma_expected.vv

@@ -0,0 +1,5 @@
+fn ok(a int) (int, string) {
+	return 11, 'hello'
+}
+
+fn main() {}

vlib/v/fmt/tests/fn_types_list_ending_with_comma_input.vv

@@ -0,0 +1,5 @@
+fn ok(a int,) (int, string,) {
+	return 11, 'hello'
+}
+
+fn main() {}

vlib/v/parser/parse_type.v

@@ -198,7 +198,7 @@ pub fn (mut p Parser) parse_multi_return_type() ast.Type {
 	p.check(.lpar)
 	mut mr_types := []ast.Type{}
 	mut has_generic := false
-	for p.tok.kind != .eof {
+	for p.tok.kind !in [.eof, .rpar] {
 		mr_type := p.parse_type()
 		if mr_type.idx() == 0 {
 			break