Cleanup of switch case flowRoot in svg endelement

We don't need this switch case due the fact we already check it
before the switch itself. I did introduce this in commit
5bd241b99b76ae7f4b3c1d4f2bcbaf7c487bb339 but it is redundant.

Change-Id: I24e8c946ef8b8f094daa248c701772e54790c9d1
Reviewed-on: https://gerrit.libreoffice.org/10317
Reviewed-by: Tomaž Vajngerl <quikee@gmail.com>
Tested-by: Tomaž Vajngerl <quikee@gmail.com>