patch 8.2.1486: Vim9: readdir() expression doesn't accept bool

Problem:    Vim9: readdir() expression doesn't accept bool.
Solution:   Merge with code for readdirex(). (closes #6737)
diff --git a/src/testdir/test_vim9_func.vim b/src/testdir/test_vim9_func.vim
index 751cd6d..ad59844 100644
--- a/src/testdir/test_vim9_func.vim
+++ b/src/testdir/test_vim9_func.vim
@@ -1386,7 +1386,8 @@
   assert_equal(2, search('bar', 'W', 0, 0, {-> val == 1}))
 enddef
 
-def Test_readdirex()
+def Test_readdir()
+   eval expand('.')->readdir({e -> e[0] !=# '.'})
    eval expand('.')->readdirex({e -> e.name[0] !=# '.'})
 enddef