[ABC Website] Remove bitdb

Summary: This infra was spun up since Raipay used it before development of Chronik. With chronik active, this has no known users. More value in focusing on chronik as the indexing solution than in supporting a legacy product.

Test Plan:
bundle exec jekyll serve --incremental
Navigate to ecash page
Make sure bitdb tile is no longer there

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Subscribers: Fabien

Differential Revision: https://reviews.bitcoinabc.org/D11675