Update duckdb index files

.gitattributes

@@ -36,3 +36,4 @@ saved_model/**/* filter=lfs diff=lfs merge=lfs -text
 *.ogg filter=lfs diff=lfs merge=lfs -text
 *.wav filter=lfs diff=lfs merge=lfs -text
 default/abstracts/index.duckdb filter=lfs diff=lfs merge=lfs -text
+abstracts[[:space:]](2021)/train/index.duckdb filter=lfs diff=lfs merge=lfs -text

abstracts (2021)/train/index.duckdb

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:2b2c35ae783982ff24e401100505ea9756d253e2cc706ce800743741776269bc
+size 1511010304