motion: Disable Motion app

This is a debugging app, not useful for most people.
Also remove the app icon.

src/displayapp/screens/ApplicationList.h

@@ -50,9 +50,11 @@ namespace Pinetime {
           {Symbols::paintbrush, Apps::Paint},
           {Symbols::paddle, Apps::Paddle},
           {"2", Apps::Twos},
-          {Symbols::chartLine, Apps::Motion},
           {Symbols::drum, Apps::Metronome},
           {Symbols::map, Apps::Navigation},
+          {Symbols::none, Apps::None},
+
+          // {"M", Apps::Motion},
         }};
         ScreenList<nScreens> screens;
       };

src/displayapp/screens/Symbols.h

@@ -34,7 +34,6 @@ namespace Pinetime {
         static constexpr const char* hourGlass = "\xEF\x89\x92";
         static constexpr const char* lapsFlag = "\xEF\x80\xA4";
         static constexpr const char* drum = "\xEF\x95\xA9";
-        static constexpr const char* chartLine = "\xEF\x88\x81";
         static constexpr const char* eye = "\xEF\x81\xAE";
         static constexpr const char* home = "\xEF\x80\x95";
         static constexpr const char* sleep = "\xEE\xBD\x84";