Update duckdb index files

.gitattributes

@@ -195,3 +195,4 @@ 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
 mao_zedong_thought/test/index.duckdb filter=lfs diff=lfs merge=lfs -text
+mao_zedong_thought/val/index.duckdb filter=lfs diff=lfs merge=lfs -text

mao_zedong_thought/val/index.duckdb

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:59766701423f4e0ae99aad183f1dfbdfb46cebea59f8140b98eb0b773534b36b
+size 1060864