Update peps/pep-0728.rst

Author: carljm

peps/pep-0728.rst

@@ -651,7 +651,7 @@ on such TypedDict types::
         reveal_type(movie.items())  # Revealed type is 'dict_items[str, str | int]'
         reveal_type(movie.values())  # Revealed type is 'dict_values[str, str | int]'
 
-By extension of this assignability rule, type chekcers may allow indexed accesses
+By extension of this assignability rule, type checkers may allow indexed accesses
 with arbitrary str keys when ``extra_items`` or ``closed=True`` is specified.
 For example::