chore: remove legacy C plugin integration (lancedb#3243)

The plugin hasn't built in over a year and the fact that we have git
submodules can cause expensive build times for downstream projects like
lancedb when they need to declare a git dependency on lance. If we need
it back later we can always revert the change.

Author: westonpace

.github/workflows/duckdb.yml

@@ -67,11 +67,6 @@ docs/api/python
 **/.ipynb_checkpoints/
 docs/notebooks
 
-
-integration/duckdb/*-build
-integration/duckdb/lance.duckdb_extension.*.zip
-
-notebooks/lance.duckdb_extension
 notebooks/sift
 notebooks/image_data/data
 benchmarks/sift/sift

.gitignore

@@ -1,6 +0,0 @@
-[submodule "integration/duckdb_lance/duckdb"]
-	path = integration/duckdb_lance/duckdb
-	url = https://github.com/duckdb/duckdb.git
-[submodule "integration/duckdb_lance/duckdb-ext/duckdb"]
-	path = integration/duckdb_lance/duckdb-ext/duckdb
-	url = https://github.com/duckdb/duckdb.git

.gitmodules

@@ -127,13 +127,6 @@ Example Notebooks
 
 Example notebooks are under `examples`. These are standalone notebooks you should be able to download and run.
 
-DuckDB Extension
-~~~~~~~~~~~~~~~~
-
-In python, Lance integrates with DuckDB via Apache Arrow. Outside of python, the highly experimental duckdb extension for Lance
-lives under `integration/duckdb_lance`. This uses the DuckDB `Rust extension framework <https://github.com/Mause/duckdb-extension-framework>`_.
-The main code lives under `integration/duckdb_lance/src`. Follow the integration README for more details.
-
 Benchmarks
 ~~~~~~~~~~