Update duckdb index files

.gitattributes

@@ -315,3 +315,4 @@ scottish_gaelic/test/index.duckdb filter=lfs diff=lfs merge=lfs -text
 russian/validation/index.duckdb filter=lfs diff=lfs merge=lfs -text
 scottish_gaelic/train/index.duckdb filter=lfs diff=lfs merge=lfs -text
 scottish_gaelic/validation/index.duckdb filter=lfs diff=lfs merge=lfs -text
+serbian_cyrillic/test/index.duckdb filter=lfs diff=lfs merge=lfs -text

serbian_cyrillic/test/index.duckdb

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:fa3290e3196c4cdf733d48ab11b5316706cf78fda3bab578020a0b892833160b
+size 4206592