Delete old duckdb index files

default/test/index.duckdb

@@ -1,3 +0,0 @@
-version https://git-lfs.github.com/spec/v1
-oid sha256:48e94a61f157772c68299f1f95d3ff58ea997540867ba47999af208bba66c520
-size 16003072

default/train/index.duckdb

@@ -1,3 +0,0 @@
-version https://git-lfs.github.com/spec/v1
-oid sha256:0ec852e048df789b5d3a94096cdc2b89779263eb34bbe0489a1efa853d67bac9
-size 77082624

default/validation/index.duckdb

@@ -1,3 +0,0 @@
-version https://git-lfs.github.com/spec/v1
-oid sha256:1957cc15f80bc23a2ebd30fcfba79431aa1e655b5f31e593838295c2e70b8def
-size 16265216