[chronik-docs] Patch dockerfile so that chronik links are not broken

Summary:
Testing CI deployments, docusaurus throws build errors in npm run build step as chronik links to chronik-client generated files are broken. This is because chronik-client did not build first. Missed bc was built locally.

Also get rid of the .abclatestversion.sample convention, and just keep a templated 0.0.0 .abclatestversion in the monorepo. This will be overwritten in CI for deployment. But, if we want to preview the site without adding any custom scripts, should have some kind of default file in place.

Test Plan:
To test preview,

./contrib/teamcity/build-configurations.py preview-chronik.e.cash

To test prod,

create .abclatestversion in docs/chronik.e.cash with contents 0.29.2

Edit line 25 of modules/Dockerfile to read ARG NGINX_CONF=nginx-preview.conf, then

docker build -t chronik-docs_local .
docker run --rm -p 8080:80 --name chronik-docs chronik-docs_local

site is available at localhost:8080, links are not broken (the build will fail if there are broken links), and download & install links use 0.29.2

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Subscribers: Fabien

Differential Revision: https://reviews.bitcoinabc.org/D16042