builtin: fix warnings for tests inside vlib/builtin/js

vlib/builtin/js/array_test.js.v

@@ -1166,7 +1166,9 @@ fn test_array_int_pop() {
 	assert a.len == 3
 	assert z == 4
 	x1 := a.pop()
+	println(x1)
 	x2 := a.pop()
+	println(x2)
 	final := a.pop()
 	assert final == 1
 }

vlib/builtin/js/int_test.js.v

@@ -99,6 +99,7 @@ fn test_hex() {
 	b := 1234
 	assert b.hex() == '4d2'
 	b1 := -1
+	println(b1)
 	// assert b1.hex() == 'ffffffff'
 	// unsigned tests
 	// assert u8(12).hex() == '0c'

vlib/builtin/js/map_test.js.v

@@ -372,6 +372,9 @@ fn test_map_assign() {
 		'r': u16(6)
 		's': 5
 	}}
+	println(a)
+	println(b)
+	println(c)
 }
 
 fn test_postfix_op_directly() {

vlib/builtin/js/string_test.js.v

@@ -1,4 +1,4 @@
-import strings
+// import strings
 
 // Copyright (c) 2019-2022 Alexander Medvednikov. All rights reserved.
 // Use of this source code is governed by an MIT license
@@ -636,6 +636,7 @@ fn test_for_loop_two() {
 
 fn test_quote() {
 	a := `'`
+	println(a)
 	println('testing double quotes')
 	b := 'hi'
 	assert b == 'hi'
@@ -727,6 +728,7 @@ fn test_raw() {
 
 fn test_raw_with_quotes() {
 	raw := r"some'" + r'"thing' // " should be escaped in the generated C code
+	println(raw)
 	// assert raw[0] == `s`
 	// assert raw[5] == `"`
 	// assert raw[6] == `t`