Delete old duckdb index files

default/test/index.duckdb

@@ -1,3 +0,0 @@
-version https://git-lfs.github.com/spec/v1
-oid sha256:77fed304dcd6eb3ae476c536ed1dc98451cc2cf38271369cba28c1beb32cb3ae
-size 194260992

default/train/index.duckdb

@@ -1,3 +0,0 @@
-version https://git-lfs.github.com/spec/v1
-oid sha256:0a63007aba5a238096c83d35483a578979c7b4793ecae368546466bb4daf048a
-size 1726754816

default/validation/index.duckdb

@@ -1,3 +0,0 @@
-version https://git-lfs.github.com/spec/v1
-oid sha256:dc9391e153f39e340e1c64991237bcb40a343118e347b23182b5bdd6e722cd35
-size 97792000