simple_shader: Clean up shaders/simple.frag, rebuild runners (#1715)

simple_shader/windows/runner/win32_window.cpp

@@ -60,7 +60,7 @@ class WindowClassRegistrar {
  public:
   ~WindowClassRegistrar() = default;
 
-  // Returns the singleton registar instance.
+  // Returns the singleton registrar instance.
   static WindowClassRegistrar* GetInstance() {
     if (!instance_) {
       instance_ = new WindowClassRegistrar();