PEP 747: Fix code block formatting. Fix grammar. (#4006)

Author: davidfstr

peps/pep-0747.rst

@@ -26,7 +26,7 @@ an overly-wide type like ``object``, which makes some use cases impossible and
 generally reduces type safety. This PEP addresses this limitation by
 introducing a new special form ``typing.TypeForm``.
 
-This PEP makes no changes to the Python grammar. ``TypeForm`` is
+This PEP makes no changes to the Python grammar. Correct usage of ``TypeForm`` is
 intended to be enforced only by type checkers, not by the Python runtime.
 
 
@@ -95,13 +95,10 @@ would benefit from ``TypeForm``:
 -  Assignability checkers:
 
    -  Determines whether a value is assignable to a specified type
-   -  Pattern 1:
-
-      ``def is_assignable[T](value: object, typx: TypeForm[T]) -> TypeIs[T]``
 
-   -  Pattern 2:
+   -  Pattern 1: ``def is_assignable[T](value: object, typx: TypeForm[T]) -> TypeIs[T]``
 
-      ``def is_match[T](value: object, typx: TypeForm[T]) -> TypeGuard[T]``
+   -  Pattern 2: ``def is_match[T](value: object, typx: TypeForm[T]) -> TypeGuard[T]``
 
    -  Examples: beartype.\ `is_bearable`_, trycast.\ `isassignable`_,
       typeguard.\ `check_type`_, xdsl.\ `isa`_
@@ -119,7 +116,9 @@ would benefit from ``TypeForm``:
 
    -  Pattern 1:
 
-      ``def convert[T](value: object, typx: TypeForm[T]) -> T``
+      ::
+
+        def convert[T](value: object, typx: TypeForm[T]) -> T
 
       -  Examples: cattrs.BaseConverter.\ `structure`_, trycast.\ `checkcast`_,
          typedload.\ `load`_