Sunset the sqlite3 binary/headers feature

[edmorley]

This buildpack has historically included the sqlite3 development headers and CLI binary in the build, (a) to support the previous way the Python runtime was built, (b) to allow the use of third party packages like pysqlite.

However:

1. Our Python runtimes now link against the sqlite library in the base image instead
2. The pysqlite package doesn't support Python 3, and the related pysqlite3 package (a) offers minimal benefits over the Python stdlib's module (so most people could/should/are using the stdlib version instead), (b) has a binary package available that doesn't need the headers (pysqlite3-binary), (c) has very low usage according to metrics.
3. Results in slower build times due to the APT download/install step - which from our metrics can vary quite a bit in duration depending on how the Ubuntu APT mirrors are doing.
4. The feature has already been dropped for the CNB.
5. The feature is already switched off when using Python 3.13+ or Poetry with the classic buildpack.

As such, we want to fully sunset it for the classic buildpack too.

GUS-W-17308963.