Update duckdb index files

.gitattributes

@@ -193,3 +193,4 @@ fire_engineer/dev/index.duckdb filter=lfs diff=lfs merge=lfs -text
 teacher_qualification/val/index.duckdb filter=lfs diff=lfs merge=lfs -text
 middle_school_physics/dev/index.duckdb filter=lfs diff=lfs merge=lfs -text
 marxism/val/index.duckdb filter=lfs diff=lfs merge=lfs -text
+modern_chinese_history/dev/index.duckdb filter=lfs diff=lfs merge=lfs -text

modern_chinese_history/dev/index.duckdb

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:9774eb1c8a78c511d6ec0b9fc1747e9d9eb7a5f3a9d4a6e0a5f3816f4cf23e85
+size 1060864