Clean up comments in root.h

Removed comments regarding input history size limitations.

src/ui/root.h

@@ -54,9 +54,6 @@ public:
   typedef std::vector<std::string> InputHistoryCategory;
   typedef std::map<int, InputHistoryCategory> InputHistory;
 
-  // Every category holds this many entries, and the whole history is written to
-  // and read back from the session, so the useful range ends long before the
-  // point where resizing it becomes a memory problem.
   static constexpr int max_input_history_size = 4096;
 
   Root();