Note Links: Considering anything which doesn't have a '://' as local

Only local notes are shown in the backlinks. Earlier our idea of local
links was notes which start with './', but now since we accept the
direct filename as well, we should support that in the backlinks as
well.

lib/core/note.dart

@@ -473,8 +473,7 @@ class Note with NotesNotifier {
         continue;
       }
 
-      var isLocal = (path.startsWith('/') || path.startsWith('.')) &&
-          !path.contains('://');
+      var isLocal = !path.contains('://');
       if (isLocal) {
         l.filePath = p.join(parent.folderPath, p.normalize(l.filePath));
         links.add(l);