Update duckdb index files

.gitattributes

@@ -60,3 +60,4 @@ pd_news/train/index.duckdb filter=lfs diff=lfs merge=lfs -text
 ccby_law/partial-train/index.duckdb filter=lfs diff=lfs merge=lfs -text
 ccby_s2orc/partial-train/index.duckdb filter=lfs diff=lfs merge=lfs -text
 ccby_stackexchange/partial-train/index.duckdb filter=lfs diff=lfs merge=lfs -text
+ccby_stackoverflow/train/index.duckdb filter=lfs diff=lfs merge=lfs -text

ccby_stackoverflow/train/index.duckdb

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:444e7fbc84e5dce89bd3d9f4bf15e4c84d76c66d47283d6d6a3089496b4a157f
+size 7520137216