Fix link

Author: smokestacklightnin

docs/index.md

@@ -556,7 +556,7 @@ ml-metadata (MLMD) | schema_version
 
 The MLMD library has a high-level API that you can readily use with your ML
 pipelines. See the
-[MLMD API documentation](api/mlmd/mlmd.md)
+[MLMD API documentation](api/mlmd/)
 for more details.
 
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