patch 8.2.0512: Vim9: no optional arguments in func type

Problem:    Vim9: no optional arguments in func type.
Solution:   Check for question mark after type.  Find function reference
            without function().
diff --git a/src/testdir/test_vim9_expr.vim b/src/testdir/test_vim9_expr.vim
index d9c20ac..f11fc83 100644
--- a/src/testdir/test_vim9_expr.vim
+++ b/src/testdir/test_vim9_expr.vim
@@ -460,8 +460,8 @@
 
   call CheckDefFailureMult(['let j: job', 'let chan: channel', 'let r = j == chan'], 'Cannot compare job with channel')
   call CheckDefFailureMult(['let j: job', 'let x: list<any>', 'let r = j == x'], 'Cannot compare job with list')
-  call CheckDefFailureMult(['let j: job', 'let x: func', 'let r = j == x'], 'Cannot compare job with func')
-  call CheckDefFailureMult(['let j: job', 'let x: func', 'let r = j == x'], 'Cannot compare job with func')
+  call CheckDefFailureMult(['let j: job', 'let Xx: func', 'let r = j == Xx'], 'Cannot compare job with func')
+  call CheckDefFailureMult(['let j: job', 'let Xx: func', 'let r = j == Xx'], 'Cannot compare job with func')
 endfunc
 
 " test addition, subtraction, concatenation