tests: conditionalize Windows difference in test-dispatch.t

The output matches the comment added 6 years ago in ef60083b5536, so I'm
assuming that difference was the reason for the over-globbing removed in
93a7539a546e.

There's still a bit of py3 instability here, but I assume those are just more
Windows issues:

  @@ -95,7 +95,7 @@
     [255]

     $ hg log -b --cwd=inexistent default
  -  abort: $ENOENT$: 'inexistent'
  +  abort: $ENOENT$: inexistent
     [255]

     $ hg log -b '--config=ui.traceback=yes' 2>&1 | grep '^Traceback'
  @@ -189,7 +189,7 @@

     $ hg -R a archive ''
     abort: $ENOENT$: '' (no-windows !)
  -  abort: $ENOTDIR$: '' (windows !)
  +  abort: $ENOTDIR$
     [255]

   #if no-outer-repo

tests/test-dispatch.t

@@ -188,7 +188,8 b' OSError "No such file or directory" / "T'
 specified" should include filename even when it is empty
 
   $ hg -R a archive ''
-  abort: $ENOENT$: ''
+  abort: $ENOENT$: '' (no-windows !)
+  abort: $ENOTDIR$: '' (windows !)
   [255]
 
 #if no-outer-repo