fix: Revert changes to adaptive card templates to support PVA

[tdurnford]

Description

Revert template changes in PR #7593 to support PVA

Task Item

Closes #7394

[cwhitten]

we don't want the use of json here, the following should work:

- ```{
  "$schema": "http://adaptivecards.io/schemas/adaptive-card.json",
  "version": "1.2",
  "type": "AdaptiveCard",
  "body": [
    {
      "type": "TextBlock",
      "text": "default text",
      "weight": "bolder",
      "isSubtle": false
    }
  ]
}```

[tdurnford]

Oh, I see. So we still want the Activity template to use${json(template_name()}, but we don't want to use json in the adaptive card template string.

[cwhitten]

Yes TJ exactly

[tdurnford]

When I exclude the json() all together, it doesn't work in the Web Chat panel. I think we still need it in the Activity template.

# SendActivity_yhVIg9()
[Activity
    Attachments = ${json(SendActivity_yhVIg9_attachment_h83mGt())}
]

# SendActivity_yhVIg9_attachment_h83mGt()
> To learn more Adaptive Cards format, read the documentation at
> https://docs.microsoft.com/en-us/adaptive-cards/getting-started/bots
- ```{
  "$schema": "http://adaptivecards.io/schemas/adaptive-card.json",
  "version": "1.2",
  "type": "AdaptiveCard",
  "body": [
    {
      "type": "TextBlock",
      "text": "default text",
      "weight": "bolder",
      "isSubtle": false
    }
  ]
}```

[cwhitten]

That's right I tested the same thing myself (edited my previous message)

[coveralls]

Coverage remained the same at 50.559% when pulling 74cbd8d on durnford/fix/pva-attachments into 8406071 on main.