Fix minor typo in MicroPython libraries page

Author: tylercrumpton

docs/library/index.rst

@@ -70,7 +70,7 @@ CircuitPython/MicroPython-specific libraries
 
 Functionality specific to the CircuitPython/MicroPython implementation is available in
 the following libraries. These libraries may change signficantly or be removed in future
-versions of CircuitPtyon.
+versions of CircuitPython.
 
 .. toctree::
    :maxdepth: 1