Fix ytext event.delta - items that are synced and deleted

When items are added and deleted in the same transaction, event.delta would recognize them as added (though they are actually deleted). Now it just ignores them.

tests/testHelper.js

@@ -360,7 +360,7 @@ export const compareDS = (ds1, ds2) => {
 /**
  * @template T
  * @param {t.TestCase} tc
- * @param {Array<function(TestYInstance,prng.PRNG,T):void>} mods
+ * @param {Array<function(Y.Doc,prng.PRNG,T):void>} mods
  * @param {number} iterations
  * @param {InitTestObjectCallback<T>} [initTestObject]
  */

tests/y-text.tests.js

@@ -27,6 +27,13 @@ export const testBasicInsertAndDelete = tc => {
   text0.delete(1, 1)
   t.assert(text0.toString() === 'b', 'Basic delete works (position 1)')
   t.compare(delta, [{ retain: 1 }, { delete: 1 }])
+
+  users[0].transact(() => {
+    text0.insert(0, '1')
+    text0.delete(0, 1)
+  })
+  t.compare(delta, [])
+
   compare(users)
 }