fix viewport size

in_one_weekend/src/main.zig

@@ -56,7 +56,7 @@ pub fn main() anyerror!void {
 
     // Camera
     const viewportHeight = 2.0;
-    const viewportWidth = @floatToInt(usize, viewportHeight * aspectRatio);
+    const viewportWidth = viewportHeight * aspectRatio;
     const focalLength = 1.0;
 
     const origin = Vec3{};