remove dead code in SwDoc::CloneSdrObj

remove dead code in SwDoc::CloneSdrObj

Dead because
    isType<SdrObject>(pObj.get()
is unconditionally true, which renders the entire if statement dead.

Ever since it was introduced in

    commit 68428bf17441dc0ec9dfcffd7cc6073660e552f0
    Author: Vladimir Glazounov <vg@openoffice.org>
    Date:   Fri Jul 4 12:19:41 2003 +0000
    INTEGRATION: CWS aig02 (1.12.32); FILE MERGED
2003/07/03 13:29:21 od 1.12.32.4: #108784# further adjustments for
support of drawing objects in header/footer
<SwDoc::CopyLayoutFmt(..)> - do *not* connect draw frame
format to
             layout, if its corresponding <MakeFrms> will not be called.
2003/07/02 16:04:01 od 1.12.32.3: #108784# - consider 'invisible'
layer at drawing page for support of
               drawing objects in header/footer
2003/06/26 18:17:53 od 1.12.32.2: #108784# - further adjustments for
support of drawing objects in header/footer
2003/06/26 17:02:11 dvo 1.12.32.1: #108784# copy shapes (but not
controls) into header/footers

Change-Id: Idca3d73ac5b790f93e56214ce1aaa3e99a173a6c
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/151141
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>