refactor(gui): drop setFullscreen now that chrome is a Lua node

Fullscreen was the firmware surrendering a strip it clipped apps out of.
The strip is a sibling node now, so an app that wants the panel is chrome
choosing not to build itself.

native/include/lua/providers.h

@@ -136,9 +136,6 @@ public:
   virtual void roundRect(int32_t x, int32_t y, int32_t w, int32_t h,
                          int32_t radius, int32_t background, const int32_t* top,
                          const int32_t* bottom, const int32_t* border) = 0;
-  // Hands the app the whole panel, including whatever chrome the firmware
-  // paints.
-  virtual void setFullscreen(bool on) = 0;
   // Applies everything drawn since the last commit. The runtime supplies only
   // the timing -- the end of a callback batch -- because that is the one fact a
   // driver cannot know; which region to touch, which waveform, and whether to