docs(input): correct getNormalSize with EXIF orientation example (#3241)

docs/api-input.md

@@ -69,7 +69,7 @@ image
 const size = getNormalSize(await sharp(input).metadata());
 
 function getNormalSize({ width, height, orientation }) {
-  return orientation || 0 >= 5
+  return (orientation || 0) >= 5
     ? { width: height, height: width }
     : { width, height };
 }