Update duckdb index files

.gitattributes

@@ -180,3 +180,4 @@ middle_school_biology/val/index.duckdb filter=lfs diff=lfs merge=lfs -text
 middle_school_biology/dev/index.duckdb filter=lfs diff=lfs merge=lfs -text
 legal_professional/val/index.duckdb filter=lfs diff=lfs merge=lfs -text
 middle_school_physics/test/index.duckdb filter=lfs diff=lfs merge=lfs -text
+modern_chinese_history/val/index.duckdb filter=lfs diff=lfs merge=lfs -text

modern_chinese_history/val/index.duckdb

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:f6080dbada68f45a8a8309c4982b44745f56c3d92f492d5ac582444143b46a7a
+size 1060864