remove some unnecessary imports and call them inline

src/image.rs

@@ -1,5 +1,3 @@
-use crate::mock;
-
 #[derive(Debug, Eq, PartialEq)]
 pub struct Image {
     pub pixels: Vec<u32>, // 64 for SD, 256 for HD
@@ -61,7 +59,7 @@ fn test_image_from_string() {
 
 #[test]
 fn test_image_to_string() {
-    let output = mock::image::chequers_1().to_string();
+    let output = crate::mock::image::chequers_1().to_string();
     let expected = include_str!("test-resources/image-chequers-1").to_string();
     assert_eq!(output, expected);
 }