patch 8.2.3240: Lua print() does not work properly

Problem:    Lua print() does not work properly.
Solution:   Put back lua_pop().
diff --git a/src/testdir/test_lua.vim b/src/testdir/test_lua.vim
index 2f20404..c30f959 100644
--- a/src/testdir/test_lua.vim
+++ b/src/testdir/test_lua.vim
@@ -870,8 +870,8 @@
 
 " Test for dealing with strings containing newlines and null character
 func Test_lua_string_with_newline()
-  let x = execute('lua print("Hello\nWorld")')
-  call assert_equal("\nHello\nWorld", x)
+  let x = execute('lua print("Hello\nWorld", 2)')
+  call assert_equal("\nHello\nWorld 2", x)
   new
   lua k = vim.buffer(vim.eval('bufnr()'))
   lua k:insert("Hello\0World", 0)