Delete old duckdb index files

default/test/index.duckdb

@@ -1,3 +0,0 @@
-version https://git-lfs.github.com/spec/v1
-oid sha256:3540e0b93a38caf83b64681558ccd9b2e9cffed133d1464097b4f5d8c5ce4dce
-size 2109440

default/train/index.duckdb

@@ -1,3 +0,0 @@
-version https://git-lfs.github.com/spec/v1
-oid sha256:fdd5398380425fc160893b228eeebd7b65f56997d29bc02f91912941ebf486ca
-size 35401728

default/validation/index.duckdb

@@ -1,3 +0,0 @@
-version https://git-lfs.github.com/spec/v1
-oid sha256:a65bdaa73ddd2c23c991705736eafd9b38a5e35ddacf50d0ac82775340345dc7
-size 2633728