Pin Contour version to v1.19.0 (#163)
Pin Contour version to v1.19.0 (#163)

Since Contour main branch started Gateway API v1alpha2 as
https://github.com/projectcontour/contour-operator/pull/456, this patch changes to pin Contour
version to v1.19.0 which supports Gateway v1alpha1.
knative-sandbox/net-gateway-api,knative-sandbox/net-gateway-api