<template type="amp-mustache"> not rendering

### Description

amp-mustache templates are not being rendering in gmail. There is a `display: none !important;` style being added to it coming from the file `/css/ampshared.css` as you can see in the screenshot bellow:

The expected behavior is to have the following from the screenshot bellow, taken from the [amp playground](https://playground.amp.dev/) with the exact same html code used in gmail.

### Reproduction Steps

using amp-mustache version 0.2 on gmail to render an json object like

```
{
"items": [
{
"fullname": "",
"carousel_items": [
{
"image_url": "",
"image_alt": "",
"redirect_link_url": ""
},
{
"image_url": "",
"image_alt": "",
"redirect_link_url": ""
},
{
"image_url": "",
"image_alt": "",
"redirect_link_url": ""
},
{
"image_url": "",
"image_alt": "",
"redirect_link_url": ""
},
{
"image_url": "",
"image_alt": "",
"redirect_link_url": ""
}
]
}
]
}
```

### Relevant Logs

_No response_

### Browser(s) Affected

_No response_

### OS(s) Affected

_No response_

### Device(s) Affected

_No response_

### AMP Version Affected

_No response_