Remove guidance against passing unique_ptr<T> by const&, closes #2240

Author: hsutter

CppCoreGuidelines.md

@@ -9993,14 +9993,9 @@ Using `unique_ptr` in this way both documents and enforces the function call's o
 
     void uses(widget*);            // just uses the widget
 
-##### Example, bad
-
-    void thinko(const unique_ptr<widget>&); // usually not what you want
-
 ##### Enforcement
 
 * (Simple) Warn if a function takes a `Unique_pointer<T>` parameter by lvalue reference and does not either assign to it or call `reset()` on it on at least one code path. Suggest taking a `T*` or `T&` instead.
-* (Simple) ((Foundation)) Warn if a function takes a `Unique_pointer<T>` parameter by reference to `const`. Suggest taking a `const T*` or `const T&` instead.
 
 ### <a name="Rr-reseat"></a>R.33: Take a `unique_ptr<widget>&` parameter to express that a function reseats the `widget`
 
@@ -10016,14 +10011,9 @@ Using `unique_ptr` in this way both documents and enforces the function call's r
 
     void reseat(unique_ptr<widget>&); // "will" or "might" reseat pointer
 
-##### Example, bad
-
-    void thinko(const unique_ptr<widget>&); // usually not what you want
-
 ##### Enforcement
 
 * (Simple) Warn if a function takes a `Unique_pointer<T>` parameter by lvalue reference and does not either assign to it or call `reset()` on it on at least one code path. Suggest taking a `T*` or `T&` instead.
-* (Simple) ((Foundation)) Warn if a function takes a `Unique_pointer<T>` parameter by reference to `const`. Suggest taking a `const T*` or `const T&` instead.
 
 ### <a name="Rr-sharedptrparam-owner"></a>R.34: Take a `shared_ptr<widget>` parameter to express shared ownership