Update duckdb index files

.gitattributes

@@ -56,3 +56,4 @@ train.csv filter=lfs diff=lfs merge=lfs -text
 validation.csv filter=lfs diff=lfs merge=lfs -text
 test.csv filter=lfs diff=lfs merge=lfs -text
 stacked-summaries--stacked-xsum-1024/test/index.duckdb filter=lfs diff=lfs merge=lfs -text
+stacked-summaries--stacked-xsum-1024/validation/index.duckdb filter=lfs diff=lfs merge=lfs -text

stacked-summaries--stacked-xsum-1024/validation/index.duckdb

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:09f69249552a9a61d3074c73d27df57424bf10804adbbfd53ea1c8b199cd1bde
+size 105656320