clang-tidy: use = default

Found with modernize-use-equals-default

Signed-off-by: Rosen Penev <rosenp@gmail.com>

src/commands/CmdBurndown.cpp

@@ -124,7 +124,7 @@ public:
   Chart (char);
   Chart (const Chart&);              // Unimplemented
   Chart& operator= (const Chart&);   // Unimplemented
-  ~Chart ();
+  ~Chart () = default;
 
   void scan (std::vector <Task>&);
   void scanForPeak (std::vector <Task>&);
@@ -184,11 +184,6 @@ Chart::Chart (char type)
   _period = type;
 }
 
-////////////////////////////////////////////////////////////////////////////////
-Chart::~Chart ()
-{
-}
-
 ////////////////////////////////////////////////////////////////////////////////
 // Scan all tasks, quantize the dates by day, and find the peak pending count
 // and corresponding epoch.

src/commands/Command.cpp

@@ -235,11 +235,6 @@ Command::Command ()
 {
 }
 
-////////////////////////////////////////////////////////////////////////////////
-Command::~Command ()
-{
-}
-
 ////////////////////////////////////////////////////////////////////////////////
 std::string Command::keyword () const
 {

src/commands/Command.h

@@ -53,7 +53,7 @@ public:
   };
 
   Command ();
-  virtual ~Command ();
+  virtual ~Command () = default;
 
   static void factory (std::map <std::string, Command*>&);