patch 8.2.1182: Vim9: no check for whitespace after comma in lambda

Problem:    Vim9: no check for whitespace after comma in lambda.
Solution:   Give error if white space is missing.
diff --git a/src/testdir/test_vim9_func.vim b/src/testdir/test_vim9_func.vim
index f09ecc9..77ada94 100644
--- a/src/testdir/test_vim9_func.vim
+++ b/src/testdir/test_vim9_func.vim
@@ -967,7 +967,7 @@
 
 def Line_continuation_in_lambda(): list<number>
   let x = range(97, 100)
-      ->map({_,v -> nr2char(v)
+      ->map({_, v -> nr2char(v)
           ->toupper()})
       ->reverse()
   return x