[mock-chronik-client] Use npm published version of ecashaddrjs as dependency for published version

Summary: The local dependency of ecashaddrjs is great for the monorepo as it ensures we always use the latest version in CI. However this breaks the published version. Since ecashaddrjs is a dependency of mock-chronik-client and not a devDependency, it's actually not even possible to npm i mock-chronik-client right now. The published version is broken.

Test Plan:
`docker build -f mock-chronik-client.Dockerfile -t mock-chronik-client_local .
docker run mock-chronik-client_local` builds

Reviewers: #bitcoin_abc, PiRK

Reviewed By: #bitcoin_abc, PiRK

Differential Revision: https://reviews.bitcoinabc.org/D17227