Bump minimum allowed version of hpack.
Bump minimum allowed version of hpack.

We need this for the raw kwarg.

python-hyper/hyper-h2,Kriechi/hyper-h2,vladmunteanu/hyper-h2,vladmunteanu/hyper-h2,bhavishyagopesh/hyper-h2,Kriechi/hyper-h2,python-hyper/hyper-h2