shell32: Increase dde_connect res value

[Vincent Povirk]

> http://bugs.winehq.org/show_bug.cgi?id=26830 is easily solved by
> http://bugs.winehq.org/attachment.cgi?id=34184 but I don't know if this will
> break anything. I cannot find a reference as to why it needs to be set to
> 256, but there must be a reason for this.

The correct solution would be to dynamically allocate a buffer of the
needed length when necessary. AFAICT we're already doing that in
dde_connect, and the patch no longer applies.