PEP 747: Fix Sphinx warnings

- #type_t reference was introduced in PR#3929, but was not used in the document text. Removed it.
- #TypeIs reference was converted from #TypeIsPep, however it is now linked in code via a `typing` reference. Removed it.
- #forward_ref_normalization reference usage was removed in PR#3929, but the reference was left behind. Since it makes little sense without the usage, removed it.

Author: Secrus

peps/pep-0747.rst

@@ -670,22 +670,10 @@ Acknowledgements
 Footnotes
 =========
 
-.. [#type_t]
-   :ref:`Type[T] <typing:type-brackets>` spells a class object
-
-.. [#TypeIs]
-   :ref:`TypeIs[T] <typing:typeis>` is similar to bool
-
 .. [#DataclassInitVar]
    ``dataclass.make_dataclass`` allows the type qualifier ``InitVar[...]``,
    so ``TypeForm`` cannot be used in this case.
 
-.. [#forward_ref_normalization]
-   Special forms normalize string arguments to ``ForwardRef`` instances
-   at runtime using internal helper functions in the ``typing`` module.
-   Runtime type checkers may wish to implement similar functions when
-   working with string-based forward references.
-
 .. [#quoted_less_common]
    Quoted annotations are expected to become less common starting in Python
    3.14 when :pep:`deferred annotations <649>` is implemented. However,