Fix NO_COLOR

Author: savannahostrowski

Doc/library/argparse.rst

@@ -647,7 +647,7 @@ are set.
 .. note::
 
    Error messages will include color codes when redirecting stderr to a
-   file. To avoid this, set the :envvar:`NO_COLOR` or :envvar:`PYTHON_COLORS`
+   file. To avoid this, set the |NO_COLOR|_ or :envvar:`PYTHON_COLORS`
    environment variable (e.g., ``NO_COLOR=1 python script.py 2> errors.txt``).
 
 .. versionadded:: 3.14