Fix tests so that they remove warning properly

tests/fuzz_tests.rs

@@ -21,7 +21,7 @@ fn decode_tiff(file: File) -> TiffResult<()> {
 #[test]
 fn oor_panic() {
     test_directory("./tests/fuzz_images/oor_panic", |file| {
-        decode_tiff(file).ok();
+        let _ = decode_tiff(file);
         true
     });
 }
@@ -36,7 +36,7 @@ fn oom_crash() {
 #[test]
 fn inf_loop() {
     test_directory("./tests/fuzz_images/inf_loop", |file| {
-        decode_tiff(file).ok();
+        let _ = decode_tiff(file);
         true
     });
 }
@@ -45,7 +45,7 @@ fn inf_loop() {
 #[test]
 fn divide_by_zero() {
     test_directory("./tests/fuzz_images/divide_by_zero", |file| {
-        decode_tiff(file).ok();
+        let _ = decode_tiff(file);
         true
     });
 }