ci: install driver manager from repo, not PyPI

[lidavidm]

e.g. in the PostgreSQL integration tests

Run ./ci/scripts/python_build.sh "$(pwd)" "$(pwd)/build"
Processing ./python/adbc_driver_postgresql
  Installing build dependencies: started
  Installing build dependencies: finished with status 'done'
  Getting requirements to build wheel: started
  Getting requirements to build wheel: finished with status 'done'
  Installing backend dependencies: started
  Installing backend dependencies: finished with status 'done'
  Preparing metadata (pyproject.toml): started
  Preparing metadata (pyproject.toml): finished with status 'done'
Collecting adbc-driver-manager (from adbc-driver-postgresql==0.0.0+gdc7572f)
  Obtaining dependency information for adbc-driver-manager from https://files.pythonhosted.org/packages/e9/b2/d176858cf8d15a79e100f62225da01e86e92155454f1b7a07c73b950ac37/adbc_driver_manager-0.5.1-cp311-cp311-manylinux_2_17_x86_64.manylinux2014_x86_64.whl.metadata
  Downloading adbc_driver_manager-0.5.1-cp311-cp311-manylinux_2_17_x86_64.manylinux2014_x86_64.whl.metadata (684 bytes)
Downloading adbc_driver_manager-0.5.1-cp311-cp311-manylinux_2_17_x86_64.manylinux2014_x86_64.whl (647 kB)
   ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 647.8/647.8 kB 22.6 MB/s eta 0:00:00
Building wheels for collected packages: adbc-driver-postgresql
  Building wheel for adbc-driver-postgresql (pyproject.toml): started
  Building wheel for adbc-driver-postgresql (pyproject.toml): finished with status 'done'
  Created wheel for adbc-driver-postgresql: filename=adbc_driver_postgresql-0.0.0+gdc7572f-py3-none-any.whl size=1542596 sha256=08bc138e29a54016632aa231b1c9bfb039c315e821ebdffd6859e0d41f47ea78
  Stored in directory: /tmp/pip-ephem-wheel-cache-u7ur5uyf/wheels/62/8b/79/ba3fc7d061061c3b8c6526c18f4fc13d6016070f5fb5ee8971
Successfully built adbc-driver-postgresql
Installing collected packages: adbc-driver-manager, adbc-driver-postgresql
Successfully installed adbc-driver-manager-0.5.1 adbc-driver-postgresql-0.0.0+gdc7572f