docs: Add Qdrant migration code snippets

[dishaprakash]

docs: Add Qdrant migration code snippets

Test Log:

PyTest log

Log for pytest command

cd samples/migrations
pytest

(venv311) (base) ➜  migrations git:(qdrant-migration) ✗ pytest 
/usr/local/google/home/vishwarajanand/github/langchain-google-alloydb-pg-python/samples/migrations/venv311/lib/python3.11/site-packages/pytest_asyncio/plugin.py:208: PytestDeprecationWarning: The configuration option "asyncio_default_fixture_loop_scope" is unset.
The event loop scope for asynchronous fixtures will default to the fixture caching scope. Future versions of pytest-asyncio will default the loop scope for asynchronous fixtures to function scope. Set the default fixture loop scope explicitly in order to avoid unexpected behavior in the future. Valid fixture loop scopes are: "function", "class", "module", "package", "session"

  warnings.warn(PytestDeprecationWarning(_DEFAULT_FIXTURE_LOOP_SCOPE_UNSET))
===================== test session starts =====================
platform linux -- Python 3.11.9, pytest-8.3.3, pluggy-1.5.0
rootdir: /usr/local/google/home/vishwarajanand/github/langchain-google-alloydb-pg-python
configfile: pyproject.toml
plugins: asyncio-0.24.0, anyio-4.7.0
asyncio: mode=Mode.STRICT, default_loop_scope=None
collected 1 item                                              

test_qdrant_migration.py 
.                                                          [100%]

=================================== 1 passed in 57.51s ====================================
(venv311) (base) ➜  migrations git:(qdrant-migration) ✗

[averikitsch]

See comments from Chroma PR

[averikitsch]

Please see any comments from Chroma PR

[vishwarajanand]

LGTM