Merge pull request Automattic#14957 from Automattic/vkarpov15/Automatticgh-14951

docs(model): add more info on acknowledged: false, specifically that Mongoose may return that if the update was empty

Author: vkarpov15

lib/model.js

@@ -3771,7 +3771,7 @@ Model.hydrate = function(obj, projection, options) {
  *     const res = await Person.updateMany({ name: /Stark$/ }, { isDeleted: true });
  *     res.matchedCount; // Number of documents matched
  *     res.modifiedCount; // Number of documents modified
- *     res.acknowledged; // Boolean indicating everything went smoothly.
+ *     res.acknowledged; // Boolean indicating the MongoDB server received the operation. This may be false if Mongoose did not send an update to the server because the update was empty.
  *     res.upsertedId; // null or an id containing a document that had to be upserted.
  *     res.upsertedCount; // Number indicating how many documents had to be upserted. Will either be 0 or 1.
  *
@@ -3811,7 +3811,7 @@ Model.updateMany = function updateMany(conditions, doc, options) {
  *     const res = await Person.updateOne({ name: 'Jean-Luc Picard' }, { ship: 'USS Enterprise' });
  *     res.matchedCount; // Number of documents matched
  *     res.modifiedCount; // Number of documents modified
- *     res.acknowledged; // Boolean indicating everything went smoothly.
+ *     res.acknowledged; // Boolean indicating the MongoDB server received the operation. This may be false if Mongoose did not send an update to the server because the update was empty.
  *     res.upsertedId; // null or an id containing a document that had to be upserted.
  *     res.upsertedCount; // Number indicating how many documents had to be upserted. Will either be 0 or 1.
  *
@@ -3849,7 +3849,7 @@ Model.updateOne = function updateOne(conditions, doc, options) {
  *     const res = await Person.replaceOne({ _id: 24601 }, { name: 'Jean Valjean' });
  *     res.matchedCount; // Number of documents matched
  *     res.modifiedCount; // Number of documents modified
- *     res.acknowledged; // Boolean indicating everything went smoothly.
+ *     res.acknowledged; // Boolean indicating the MongoDB server received the operation.
  *     res.upsertedId; // null or an id containing a document that had to be upserted.
  *     res.upsertedCount; // Number indicating how many documents had to be upserted. Will either be 0 or 1.
  *