msgpack,json,yaml: fix section anchors

doc/reference/reference_lua/json.rst

@@ -223,7 +223,7 @@ results:
     You must not change entries of ``decode()`` result's table metatable, because it affects all results
     and may lead to undefined behavior of other code. See :ref:`Yaml <yaml-cfg>` for a detailed example.
 
-    .. _json-module_cfg_sparse:
+.. _json-module_cfg_sparse:
 
 **Sparse arrays features:**
 

doc/reference/reference_lua/msgpack.rst

@@ -475,7 +475,7 @@ with the MsgPack format name and encoding on the right.
     You must not change entries of ``decode()`` result's table metatable, because it affects all results
     and may lead to undefined behavior of other code. See :ref:`Yaml <yaml-cfg>` for a detailed example.
 
-    .. _msgpack-cfg_sparse:
+.. _msgpack-cfg_sparse:
 
 **Sparse arrays features**
 

doc/reference/reference_lua/yaml.rst

@@ -199,7 +199,7 @@ Do not change the metatable like this.
       ...
     ...
 
-    .. _yaml-cfg_sparse:
+.. _yaml-cfg_sparse:
 
 **Sparse arrays features:**