`formula` property filters accept `string` instead of `text`.

[KoditkarVedant]

Rollup property filters must now be constructed with the string keyword instead of the text keyword if the value of the formula is a string.

Put concretely, if a page's formula property is rendered like so:

"formula property": {
    "id": "m%5D%3F%5C",
    "type": "formula",
    "formula": {
        "type": "string",
        "string": "update text 2,another text"
    }
}

This filter will no longer work in version 2022-02-22:

{
    "filter": {
        "property": "formula property",
        "formula": {
            "text": {
                "contains": "update text"
            }
        }
    }
}

Instead, write this:

{
    "filter": {
        "property": "formula property",
        "formula": {
            "string": {
                "contains": "update text"
            }
        }
    }
}

Notion changelog: https://developers.notion.com/changelog/releasing-notion-version-2022-02-22