Description

Across different documentation updateMany differs:

In: 

https://github.com/mongodb/docs/blob/v4.2/source/tutorial/update-documents.txt

https://github.com/mongodb/docs/blob/v4.2/source/reference/method/db.collection.updateMany.txt

Somewherre is shown as:

```js 

db.<collection>.updateMany({}, {$set: {a: 1);}}

```

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and somewhere as with brackets `[]`:

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```js

db.<collection>.updateMany({}, [ {$set: {a: 1 ]);}}

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Additionally, Mongoose documentation is missing about this command, and using the case without brackets silently changes no document.

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Scope of changes

Impact to Other Docs

MVP (Work and Date)

Resources (Scope or Design Docs, Invision, etc.)