[mock-chronik-client] Patch issue with aCI deployments of mock-chronik-client

Summary:
Missed this when moving repos over to local deps instead of npmjs.

The dockerfile here is copying the full monorepo into the mock-chronik-client workdir, instead of just the mock-chronik-client dir.

This causes publication of the whole monorepo as a module to (thankfully) fail as the npm publish auth is then not at the expected dir level.

Test Plan:
Review and sanity check. Can fully test locally but can't really test this without CI, as the credential is required to publish.

Can confirm we are trying to publish the right thing tho.

Change line 31 to CMD [ "npm", "publish", "--dry-run"]

docker build -f mock-chronik-client.Dockerfile -t mock-chronik-client_local .
docker run mock-chronik-client_local

output:

npm notice === Tarball Details ===
npm notice name:          mock-chronik-client
npm notice version:       1.9.0
npm notice filename:      mock-chronik-client-1.9.0.tgz
npm notice package size:  10.6 kB
npm notice unpacked size: 57.1 kB
npm notice shasum:        918ea19edadde5163538ee324a8022e22a259e23
npm notice integrity:     sha512-jyiv+DDhmv0fv[...]azqrcjcl19gUA==
npm notice total files:   7
npm notice
npm WARN This command requires you to be logged in to https://registry.npmjs.org/ (dry-run)
npm notice Publishing to https://registry.npmjs.org/ with tag latest and default access (dry-run)
+ mock-chronik-client@1.9.0

in line with what is published currently.

compare to CI error unpacked size: 100.7 MB

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D16227