Docs: clarify PYTHONDONTWRITEBYTECODE behavior

Author: Javed-Shekh777

Doc/using/cmdline.rst

@@ -880,9 +880,9 @@ conflict.
 
 .. envvar:: PYTHONDONTWRITEBYTECODE
 
-   If this is set to a value other than ``"0"``, Python won't try to write
-   ``.pyc`` files on the import of source modules. Setting it to ``"0"``
-   does not disable bytecode writing. This is equivalent to specifying the
+   If this is set to a non-empty string other than ``0``, Python won't try to write
+   ``.pyc`` files on the import of source modules. Setting it to ``0`` does
+   not disable bytecode writing. This is equivalent to specifying the
    :option:`-B` option.