`<template>` without `type` not allowed

### Description

`amphtml-validator` will currently fail when a `` without a `type` is rendered with two errors:
1. The mandatory attribute 'type' is missing in tag 'template'.
2. The tag 'template' requires including the 'amp-mustache' extension JavaScript.

It's unclear from the [linked documentation](https://amp.dev/documentation/components/amp-mustache) why this is a validation error.

React uses `` to inform the browser to throttle rendering until that element is streamed in (see https://github.com/ampproject/amphtml/issues/40279).

### Reproduction Steps

Validate
```html

another page

```

### Relevant Logs

```shell
The mandatory attribute 'type' is missing in tag 'template'.
https://amp.dev/documentation/components/amp-mustache
The tag 'template' requires including the 'amp-mustache' extension JavaScript. https://amp.dev/documentation/components/amp-mustache
```

### Browser(s) Affected

_No response_

### OS(s) Affected

_No response_

### Device(s) Affected

_No response_

### AMP Version Affected

_No response_