Fix screenshot dimensions when at 1x scale

This was regressed by ART.
Prior to ART, the screenshots were saved at the title's framebuffer resolution. A misunderstanding of the existing logic led to screenshot dimensions becoming dependent on the host render window size.

This changes the behavior to match how it was prior to ART at 1x, with screenshots now always being the title's framebuffer dimensions scaled by the resolution scaling factor.

src/video_core/video_core.cpp

@@ -55,10 +55,4 @@ std::unique_ptr<Tegra::GPU> CreateGPU(Core::Frontend::EmuWindow& emu_window, Cor
     }
 }
 
-float GetResolutionScaleFactor(const RendererBase& renderer) {
-    return Settings::values.resolution_info.active
-               ? Settings::values.resolution_info.up_factor
-               : renderer.GetRenderWindow().GetFramebufferLayout().GetScalingRatio();
-}
-
 } // namespace VideoCore

src/video_core/video_core.h

@@ -25,6 +25,4 @@ class RendererBase;
 /// Creates an emulated GPU instance using the given system context.
 std::unique_ptr<Tegra::GPU> CreateGPU(Core::Frontend::EmuWindow& emu_window, Core::System& system);
 
-float GetResolutionScaleFactor(const RendererBase& renderer);
-
 } // namespace VideoCore