fix: undo invalid refactoring (#124)

The pattern matching changed the behavior of the code into the wrong one.
See #116 (comment)

Notice the refactor operator did warn this might not be a correct refactoring:
![afbeelding](https://github.com/have-fun-was-taken/yafc-ce/assets/4461459/5a3702fb-6326-418a-9777-b538867db8de)

Yafc/Windows/ProjectPageSettingsPanel.cs

@@ -205,7 +205,7 @@ public static void LoadProjectPageFromClipboard() {
                 deflateStream.CopyTo(ms);
                 byte[] bytes = ms.GetBuffer();
                 int index = 0;
-                if (DataUtils.ReadLine(bytes, ref index) is not "YAFC" or not "ProjectPage") {
+                if (DataUtils.ReadLine(bytes, ref index) != "YAFC" || DataUtils.ReadLine(bytes, ref index) != "ProjectPage") {
                     throw new InvalidDataException();
                 }