pRg is a paragraph range, not a character range.
AnimationExporter::getTargetElementShape is still
used by the ppt export filter, so I just moved the
relevant parts over to
PowerPointExport::WriteAnimationTarget.

Change-Id: If477013d62483d57fe142c9da3ab0c75872733af
Reviewed-on: https://gerrit.libreoffice.org/40979Reviewed-by: Tamás Zolnai <tamas.zolnai@collabora.com>
Tested-by: Tamás Zolnai <tamas.zolnai@collabora.com>