Clientiface: remove "value is dummy" from docs

Commit

6a1670dbc31cc0e44178bbd9ad34ff0d5981a060 "Migrate to STL containers/algorithms."

has replaced core::map<T, bool> with std::set<T>, but didn't update
the accompanying comment saying "value is dummy". This happened at
two places.

src/clientiface.h

@@ -322,7 +322,6 @@ public:
 
 	/*
 		List of active objects that the client knows of.
-		Value is dummy.
 	*/
 	std::set<u16> m_known_objects;
 
@@ -377,7 +376,7 @@ private:
 		- A block is cleared from here when client says it has
 		  deleted it from it's memory
 
-		Key is position, value is dummy.
+		List of block positions.
 		No MapBlock* is stored here because the blocks can get deleted.
 	*/
 	std::set<v3s16> m_blocks_sent;