Delete old duckdb index files

default/train/index.duckdb

@@ -1,3 +0,0 @@
-version https://git-lfs.github.com/spec/v1
-oid sha256:a7d6c34a217ed3e273cf12a1d6f993e8d26760666b0ebb1a01807817296d6962
-size 17838080

default/validation/index.duckdb

@@ -1,3 +0,0 @@
-version https://git-lfs.github.com/spec/v1
-oid sha256:85745862527e1f7db6e3ef23936986b39cbbfa272951dd2bb791233b00124934
-size 7614464