[ecash-agora] Patch CI for prod install of ecash-wallet

Summary:
Now that it is not a dev dep, needs to be installed as a real dep

I tried to simply omit the "-D" in the ecash-wallet install, but the strange error about ecash-lib being unavailable persisted (could recreate what I see in CI locally).

With this change, it builds locally. This is (probably) a better way to do it, removing all local deps and evidence of them and then regenerating a package-lock.json with an npm install

I am not sure exactly what is causing the npm install ecash-lib@latest failure. I can do that locally. But the docker container doesn't like it.

Test Plan:
docker build -f ecash-agora.Dockerfile -t ecash-agora_local .

Re-run CI to publish a new version

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Subscribers: Fabien

Differential Revision: https://reviews.bitcoinabc.org/D18853