Change the type of the Textarea field

[kienstra]

Changes

• Changes the Textarea field ->type from textarea to string
• The ->type is for the data type of attribute that the block should accept, not for the control type like 'textarea' or 'multiselect'
• Fixes https://wordpress.org/support/topic/the-rest_validate_value_from_schema-function-was-called-incorrectly-2/

Steps to reproduce

1. Create a new block with a Textarea field
2. Publish it
3. Add it to the block editor
4. Expected: there's no notice
5. Actual: this notice shows for about a second, then disappears:

Testing instructions for this PR

1. Create a new block with 3 Textarea fields
2. For the first Textarea, set New Lines > Automatically add paragraphs
3. For the second, set New Lines > Automatically add linebreaks
4. For the third, set New Lines > No formatting
5. Publish it
6. Add it to the block editor
7. Expected: there's no PHP notice anymore
8. Expected: the linebreak and newline behavior is the same as before

[kienstra]

Hi @lukecarbis,
Could you please review this? Thanks!

[mindctrl]

Looks good!

[nickcernis]

Confirmed no “"type" schema keyword for can only be one of the built-in types” message for a new custom block with textarea fields.

[kienstra]

Thanks!