Delete old duckdb index files

mnist_ambiguous/test/index.duckdb

@@ -1,3 +0,0 @@
-version https://git-lfs.github.com/spec/v1
-oid sha256:ae9de98e2dc03489393cb40a9253f3a39e86b149ba6fddfcfe8934ee46aab97e
-size 6565888

mnist_ambiguous/test_mixed/index.duckdb

@@ -1,3 +0,0 @@
-version https://git-lfs.github.com/spec/v1
-oid sha256:dd997033245dc6cba973451839cfe75dbb36816c3837983aab45f7c06c8479d5
-size 9711616

mnist_ambiguous/train/index.duckdb

@@ -1,3 +0,0 @@
-version https://git-lfs.github.com/spec/v1
-oid sha256:765dd095087f3264a6289fc9b36472d07d5c02a5404632f2edf9a66f85a17980
-size 6565888

mnist_ambiguous/train_mixed/index.duckdb

@@ -1,3 +0,0 @@
-version https://git-lfs.github.com/spec/v1
-oid sha256:d4c505d32254c490d621b86a37b2e337f1565c7a2c7ae4589da5bc65d9406d5c
-size 25178112