Fix "useable" typo in docs (python#127200)

Fix typo in docs

Author: StanFromIreland

README.rst

@@ -64,7 +64,7 @@ the executable is called ``python.exe``; elsewhere it's just ``python``.
 Building a complete Python installation requires the use of various
 additional third-party libraries, depending on your build platform and
 configure options.  Not all standard library modules are buildable or
-useable on all platforms.  Refer to the
+usable on all platforms.  Refer to the
 `Install dependencies <https://devguide.python.org/getting-started/setup-building.html#build-dependencies>`_
 section of the `Developer Guide`_ for current detailed information on
 dependencies for various Linux distributions and macOS.