Fix typo, reference signatures from Type/Sub (closes #2625).

Author: cfa

doc/Type/Method.pod6

@@ -7,7 +7,7 @@
     class Method is Routine { }
 
 A type for methods that behave the same way then L<Routine|/type/Routine> with
-some exceptions listed in the following. For details of a methods parameter
+some exceptions listed in the following. For details of a method's parameter
 list see L<Signature|/type/Signature>.
 
 To create a method outside a L<class definition|/language/typesystem#Methods>,

doc/Type/Sub.pod6

@@ -10,6 +10,7 @@ A type for subroutines and operators. Subs are created with the C<sub>
 declarator keyword followed by an optional
 L<identifier|/language/syntax#Identifiers>. This
 L<short tutorial explains how operators are declared|/language/optut>.
+For details of a sub's parameter list see L<Signature|/type/Signature>.
 
 Note that subs that go by the same name as
 L<coercers|/language/typesystem#Coercion> will not take precedence over