No need to install backend build deps when building the front-end, and
vice versa. The build scripts (build_spark.cmd, build_sparkd.sh, etc.)
automatically install only the necessary requirements now.
Note: We'll keep the monolith requirements.txt file around (at least for
now), as it includes more than just build deps (e.g., numpy, pandas, and
jupyter for data analysis; pybit for bybit plugins, etc.).
John Colvin