Platform: remove a TODO for "proper SDL2 support" in Emscripten.

There is one already, and I'm not going to use because it's bloated.
Plus there's EmscriptenApplication that doesn't have to pay for the
extra overhead of wrapping HTML5 APIs in SDL APIs.

src/Magnum/Platform/Sdl2Application.cpp

@@ -482,7 +482,6 @@ bool Sdl2Application::tryCreate(const Configuration& configuration, const GLConf
     SDL_GL_SetAttribute(SDL_GL_FRAMEBUFFER_SRGB_CAPABLE, glConfiguration.isSrgbCapable());
     #endif
 
-    /** @todo Remove when Emscripten has proper SDL2 support */
     #ifndef CORRADE_TARGET_EMSCRIPTEN
     /* Scale window based on DPI */
     _dpiScaling = dpiScaling(configuration);