Docs: Fix incorrect sphinx markup for a class member (GH-130970)

Author: koyuki7w

Doc/library/dis.rst

@@ -535,7 +535,7 @@ details of bytecode instructions as :class:`Instruction` instances:
       :class:`dis.Positions` object holding the
       start and end locations that are covered by this instruction.
 
-   .. data::cache_info
+   .. data:: cache_info
 
       Information about the cache entries of this instruction, as
       triplets of the form ``(name, size, data)``, where the ``name``