schema CHANGE remove lysp_type_free() from the public API

Right now it is not possible to remove the parsed schema by the caller.
diff --git a/src/tree_schema_free.c b/src/tree_schema_free.c
index 4026c7f..e019972 100644
--- a/src/tree_schema_free.c
+++ b/src/tree_schema_free.c
@@ -410,7 +410,7 @@
     free(node);
 }
 
-API void
+void
 lysp_module_free(struct lysp_module *module)
 {
     struct ly_ctx *ctx;