Update duckdb index files

.gitattributes

@@ -69,3 +69,4 @@ NIH[[:space:]]ExPorter/test/index.duckdb filter=lfs diff=lfs merge=lfs -text
 ArXiv/partial-test/index.duckdb filter=lfs diff=lfs merge=lfs -text
 BookCorpus2/partial-test/index.duckdb filter=lfs diff=lfs merge=lfs -text
 DM[[:space:]]Mathematics/partial-test/index.duckdb filter=lfs diff=lfs merge=lfs -text
+DM[[:space:]]Mathematics/partial-train/index.duckdb filter=lfs diff=lfs merge=lfs -text

DM Mathematics/partial-train/index.duckdb

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:9e1eed660631d934217d14bb719d955a82001f2ca42b4fd3d8c9143d0abd0fdc
+size 2741776384