Delete old duckdb index files

default/test/index.duckdb

@@ -1,3 +0,0 @@
-version https://git-lfs.github.com/spec/v1
-oid sha256:0f1d894884637b4bb92189b54d6c961faf6044d3005ab84a3f489223d7162795
-size 1847296

default/train/index.duckdb

@@ -1,3 +0,0 @@
-version https://git-lfs.github.com/spec/v1
-oid sha256:e2936234988f5a4648c15c55ebe5170b023029de001a81133ec600a3995d2d5a
-size 85471232

default/validation/index.duckdb

@@ -1,3 +0,0 @@
-version https://git-lfs.github.com/spec/v1
-oid sha256:97863833d7c3df48fa40f6d22c382c8fdd91cd2d02b88880ac71c6285d6f13fe
-size 1323008