Replace issue-426 test

tests/reduction.rs

@@ -938,6 +938,18 @@ fn grayscale_alpha_8_should_be_grayscale_trns_1() {
     );
 }
 
+#[test]
+fn grayscale_trns_8_should_be_grayscale_1() {
+    test_it_converts(
+        "tests/files/grayscale_trns_8_should_be_grayscale_1.png",
+        true,
+        GRAYSCALE,
+        BitDepth::Eight,
+        GRAYSCALE,
+        BitDepth::One,
+    );
+}
+
 #[test]
 fn small_files() {
     test_it_converts(

tests/regression.rs

@@ -226,30 +226,6 @@ fn issue_182() {
     );
 }
 
-#[test]
-fn issue_426_01() {
-    test_it_converts(
-        "tests/files/issue-426-01.png",
-        None,
-        GRAYSCALE,
-        BitDepth::Eight,
-        GRAYSCALE,
-        BitDepth::One,
-    );
-}
-
-#[test]
-fn issue_426_02() {
-    test_it_converts(
-        "tests/files/issue-426-02.png",
-        None,
-        GRAYSCALE,
-        BitDepth::Eight,
-        GRAYSCALE,
-        BitDepth::One,
-    );
-}
-
 #[test]
 fn issue_553() {
     let png = test_it_converts(