Delete old duckdb index files

default/test/index.duckdb

@@ -1,3 +0,0 @@
-version https://git-lfs.github.com/spec/v1
-oid sha256:a591b96b3ae1cd7e74274d5017713fe1a113b0a63c18ca75c6f12e4838b0c7d0
-size 54800384

default/train/index.duckdb

@@ -1,3 +0,0 @@
-version https://git-lfs.github.com/spec/v1
-oid sha256:6c8d398fccea45f269203f1c9fe6ba81ec8c8648dc84d64182157fe35b718128
-size 969945088

default/validation/index.duckdb

@@ -1,3 +0,0 @@
-version https://git-lfs.github.com/spec/v1
-oid sha256:949af2880e82ce36a5f95ad60dfbaa94b627e8ca5215c585cba7f2bc21dc732f
-size 56373248