patch 8.2.1328: no space allowed before comma in list

Problem:    No space allowed before comma in list.
Solution:   Legacy Vim script allows it. (closes #6577)
diff --git a/src/testdir/test_listdict.vim b/src/testdir/test_listdict.vim
index beeda2f..563c79f 100644
--- a/src/testdir/test_listdict.vim
+++ b/src/testdir/test_listdict.vim
@@ -23,6 +23,9 @@
   call assert_equal(10, x)
 endfunc
 
+" This was allowed in legacy Vim script
+let s:list_with_spaces = [1 , 2 , 3]
+
 " List slices
 func Test_list_slice()
   let l = [1, 'as''d', [1, 2, function("strlen")], {'a': 1},]
@@ -202,6 +205,10 @@
   call assert_fails("let d={'k' : i}", 'E121:')
 endfunc
 
+" This was allowed in legacy Vim script
+let s:dict_with_spaces = {'one' : 1 , 'two' : 2 , 'three' : 3}
+let s:dict_with_spaces_lit = #{one : 1 , two : 2 , three : 3}
+
 " Dictionary identity
 func Test_dict_identity()
   let d = {001: 'asd', 'b': [1, 2, function('strlen')], -1: {'a': 1},}