Delete old duckdb index files

default/train/index.duckdb

@@ -1,3 +0,0 @@
-version https://git-lfs.github.com/spec/v1
-oid sha256:51dbe14034083fc134243e104fa7ff8ac396e83e4cd89716fee8b0ded3ceb64a
-size 24653824

default/validation/index.duckdb

@@ -1,3 +0,0 @@
-version https://git-lfs.github.com/spec/v1
-oid sha256:3735e529a8b3032935adb068f78cc7cd173fde9035969107a0db0cf3e23d2f59
-size 18624512