Fix regression: Linear filter persistence

This fixes #1013 by axing the use of SDL_HINT_RENDER_SCALE_QUALITY and
instead using SDL_SetTextureScaleMode.

The hint is unwieldy to use, and since #923, has resulted in a
regression where starting the game in filtered mode then switching to
nearest results in scaled textures still being filtered.

The proper solution is to use SDL_SetTextureScaleMode on the two
textures that are drawn to the final screen: gameTexture and
tempShakeTexture.

desktop_version/src/Graphics.cpp

@@ -194,6 +194,16 @@ void Graphics::create_buffers(void)
 #undef CREATE_SCROLL_TEXTURE
 #undef CREATE_TEXTURE
 #undef CREATE_TEXTURE_WITH_DIMENSIONS
+
+    SDL_SetTextureScaleMode(
+        gameTexture,
+        gameScreen.isFiltered ? SDL_ScaleModeLinear : SDL_ScaleModeNearest
+    );
+
+    SDL_SetTextureScaleMode(
+        tempShakeTexture,
+        gameScreen.isFiltered ? SDL_ScaleModeLinear : SDL_ScaleModeNearest
+    );
 }
 
 void Graphics::destroy_buffers(void)