MC19 connector: Use Docker image from model repository

The model image is now being published to https://github.com/modelingcovid/covidmodel/packages/222225.
Obtain the image from that repository instead of model-runner.
Upgrade to the latest version to fix errors caused by scenarios hardcoding May 11.

Author: adityasharad

packages/modelingcovid-covidmodel/.env

@@ -1 +1 @@
-MC19_VERSION=2e3044525
+MC19_VERSION=bd61fb8

packages/modelingcovid-covidmodel/Dockerfile

@@ -1,6 +1,6 @@
 ARG MC19_VERSION=latest
 # This image is based on https://github.com/arnoudbuzing/wolfram-engine-docker.
-FROM docker.pkg.github.com/covid-modeling/model-runner/mc19:${MC19_VERSION} AS build
+FROM docker.pkg.github.com/modelingcovid/covidmodel/mc19:${MC19_VERSION} AS build
 
 # The model repo code in the image is at this location,
 # which is used when resolving relative paths.