Update pep-0827.rst

Fix typo in class Param

Author: korbash

peps/pep-0827.rst

@@ -379,7 +379,7 @@ We introduce a ``Param`` type that contains all the information about a function
     class Param[N: str | None, T, Q: ParamQuals = typing.Never]:
         pass
 
-    ParamQuals = typing.Literal["*", "**", "default", "keyword"]
+    ParamQuals = typing.Literal["*", "**", "default", "keyword", "positional"]
 
     type PosParam[N: str | None, T] = Param[N, T, Literal["positional"]]
     type PosDefaultParam[N: str | None, T] = Param[N, T, Literal["positional", "default"]]