Added vtr-xml-utils to requirements.txt
Added vtr-xml-utils to requirements.txt

Signed-off-by: Maciej Kurc <572803cc6e8d7bb35033942e4b03254951a2e0d6@antmicro.com>

SymbiFlow/python-symbiflow-v2x,SymbiFlow/python-symbiflow-v2x