Delete old duckdb index files

default/test/index.duckdb

@@ -1,3 +0,0 @@
-version https://git-lfs.github.com/spec/v1
-oid sha256:55182d441ec7577942806007a002e2b06a6925f3338ec082a124824ffdbf469d
-size 1323008

default/train/index.duckdb

@@ -1,3 +0,0 @@
-version https://git-lfs.github.com/spec/v1
-oid sha256:34c5cc7c2183420401d7393d28c661002479d24f0c223a5b387f8fd8e115de09
-size 2371584

default/validation/index.duckdb

@@ -1,3 +0,0 @@
-version https://git-lfs.github.com/spec/v1
-oid sha256:cc95581da833f9dcef64772e1d0874fd129ab7ecff65d25e57e404b5877c8b5b
-size 1323008