[terraform] Avoid including Terraform state and secrets in keyserver Docker images

Summary: This addresses part 1 of ENG-8869.

Test Plan:

1. Docker build: docker build --build-arg HOST_GID=20 --build-arg HOST_UID=501 --build-arg COMM_JSONCONFIG_secrets_alchemy='{"key":"<secret>"}' --build-arg COMM_JSONCONFIG_secrets_walletconnect='{"key":"<secret>"}' --build-arg COMM_JSONCONFIG_secrets_neynar='{"key":"<secret>"}' --build-arg COMM_JSONCONFIG_secrets_geoip_license='{"key":"<secret>"}' --platform linux/arm64 -f keyserver/Dockerfile -t commapp/keyserver:sometag .
2. Open the build: docker run -it commapp/keyserver:sometag bash
3. Search for passwords via cd .. && (grep -R password_string . | grep -v node_modules)

Reviewers: will, bartek, varun

Reviewed By: bartek, varun

Subscribers: tomek

Differential Revision: https://phab.comm.dev/D12823