Update duckdb index files

.gitattributes

@@ -5,3 +5,4 @@ citesum/train/0000.parquet filter=lfs diff=lfs merge=lfs -text
 citesum/validation/0000.parquet filter=lfs diff=lfs merge=lfs -text
 citesum/test/0000.parquet filter=lfs diff=lfs merge=lfs -text
 citesum/train/index.duckdb filter=lfs diff=lfs merge=lfs -text
+citesum/validation/index.duckdb filter=lfs diff=lfs merge=lfs -text

citesum/validation/index.duckdb

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:6dfa000be63e14bb498c8391c4eb4d6c6daf25aaa19ff9d91d337fbd592e6fd9
+size 18362368