[token-server] Update dockerfile for ecash-lib deployment

Summary: I forgot to do this as part of D16555

Test Plan: docker build -f token-server.Dockerfile -t token-server_local . and build completes

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D16612