Fix bug in pkg:observe (observable_list.remove(Object))

pkg/observe/lib/src/observable_list.dart

Index: pkg/observe/lib/src/observable_list.dart
diff --git a/pkg/observe/lib/src/observable_list.dart b/pkg/observe/lib/src/observable_list.dart
index bc66ea02f3f529aec48e2c4aa46819d43f061118..20213749eecf2eadc606b89e7f4fbf638b90e445 100644
--- a/pkg/observe/lib/src/observable_list.dart
+++ b/pkg/observe/lib/src/observable_list.dart
@@ -102,7 +102,7 @@ class ObservableList<E> extends _ListBaseWorkaround with ObservableMixin
   bool remove(Object element) {
     for (int i = 0; i < this.length; i++) {
       if (this[i] == element) {
-        removeRange(i, 1);
+        removeRange(i, i + 1);
         return true;
       }
     }