small typo

Thanks Tiago!

Author: rocky

CHANGES.rst

@@ -21,7 +21,7 @@ A number of Built-in functions that were implemented were not accessible for var
 
 Mathics3 Modules are better integrated into the documentation.
 Existing Mathics3 modules ``pymathics.graph`` and ``pymathics.natlang`` have
-had a major overhaul, although more is needed. And will continue after th 6.0.0 release
+had a major overhaul, although more is needed. And will continue after the 6.0.0 release
 
 We have gradually been rolling in more Python type annotations and
 current Python practices such as using ``isort``, ``black`` and ``flake8``.