testautomation: fixed incorrect test.

The test was doing this:

- The output size is 80x60
- The logical size is 40x30
- The viewport is { 10, 7, 40, 30 }
- Draw to fill this whole viewport.

This would offset the filled rectangle a little, as before, but then the
viewport was the size of the entire logical space, so it wasn't a rectangle
centered in the middle of the output, as was expected.

This used to produce the expected output before the fix in
fa7a529912. But it appears the test was
incorrect, so this tweaks the viewport to produce the expected result.

test/testautomation_render.c

@@ -1149,8 +1149,8 @@ static int SDLCALL render_testLogicalSize(void *arg)
     CHECK_FUNC(SDL_SetRenderLogicalPresentation, (renderer, w / factor, h / factor, SDL_LOGICAL_PRESENTATION_LETTERBOX))
     viewport.x = (TESTRENDER_SCREEN_W / 4) / factor;
     viewport.y = (TESTRENDER_SCREEN_H / 4) / factor;
-    viewport.w = TESTRENDER_SCREEN_W / factor;
-    viewport.h = TESTRENDER_SCREEN_H / factor;
+    viewport.w = (TESTRENDER_SCREEN_W / 2) / factor;
+    viewport.h = (TESTRENDER_SCREEN_H / 2) / factor;
     CHECK_FUNC(SDL_SetRenderViewport, (renderer, &viewport))
     CHECK_FUNC(SDL_SetRenderDrawColor, (renderer, 0, 255, 0, SDL_ALPHA_OPAQUE))
     CHECK_FUNC(SDL_RenderFillRect, (renderer, NULL))