Remove python_tools/cbdep

cbdep is now distributed via PyPI and can be installed using `uv` or
`pip`, so we no longer want to do manifest-driven builds.

Change-Id: Idf08ffd0d336bf5bb5886925dbb2cca5297da2e2
Reviewed-on: https://review.couchbase.org/c/manifest/+/221552
Tested-by: Chris Hillery <[email protected]>
Reviewed-by: Ming Ho <[email protected]>

Author: ceejatec