All attributes of a custom Page Builder block are required, regardless of whether they have validators set or not.

Steps to reproduce
1. Create a custom block with the following attributes:

attributes:
    integer:
        type: integer
    text:
        type: text
        validators:
            not_blank:
                message: 'Something'

2. Create a Page and drag the new block to it.
3. Open the block's configuration.

Expected result
The 'text' attribute is marked with an asterisk and required, the 'integer' attibute is not.

Actual result
Both attributes are marked with an asterisk and required.