Fix compilation via move

[dentiny]

I met a few compilation failures, for example:

/home/ubuntu/duckpgq-extension/src/core/functions/function_data/weakly_connected_component_function_data.cpp:33:10: error: could not convert 'result' from 'unique_ptr<duckpgq::core::WeaklyConnectedComponentFunctionData,default_delete<duckpgq::core::WeaklyConnectedComponentFunctionData>,[...]>' to 'unique_ptr<duckdb::FunctionData,default_delete<duckdb::FunctionData>,[...]>'
   33 |   return result;
      |          ^~~~~~
      |          |
      |          unique_ptr<duckpgq::core::WeaklyConnectedComponentFunctionData,default_delete<duckpgq::core::WeaklyConnectedComponentFunctionData>,[...]>

Similar to the issue raised in pg_duckdb: duckdb/pg_duckdb#455

[Dtenwolde]

Hi there, thanks for the PR! I wasn't aware of these build failures but thank you for fixing them :)