bpo-44135: [docs] Fix inline markup (GH-28095)

Doc/library/functions.rst

diff --git a/Doc/library/functions.rst b/Doc/library/functions.rst
index fef6c62..9629ace 100644
--- a/Doc/library/functions.rst
+++ b/Doc/library/functions.rst
@@ -916,7 +916,7 @@
    Return ``True`` if *class* is a subclass (direct, indirect, or :term:`virtual
    <abstract base class>`) of *classinfo*.  A
    class is considered a subclass of itself. *classinfo* may be a tuple of class
-   objects or a :ref:`types-union`, in which case return True if *class* is a
+   objects or a :ref:`types-union`, in which case return ``True`` if *class* is a
    subclass of any entry in *classinfo*.  In any other case, a :exc:`TypeError`
    exception is raised.