Added a legal disclaimer about the "date_of_birth" customer attribute

[jeff-matthews]

Purpose of this pull request

This pull request (PR) adds a legal disclaimer to places in the docs where we reference the date_of_birth attribute of the customer database entity.

• See internal ticket DOC-244 for more details.
• See internal staging build #138 for HTML preview.

The dob attribute exists in the REST API reference docs as well, however, we will address that separately from this pull request.

Affected DevDocs pages

• https://devdocs.magento.com/compliance/privacy/pi-data-reference-m2.html#customer-data
• https://devdocs.magento.com/guides/v2.4/config-guide/prod/config-reference-most.html#customer-configuration-paths
• https://devdocs.magento.com/guides/v2.3/config-guide/prod/config-reference-most.html#customer-configuration-paths
• https://devdocs.magento.com/guides/v2.4/extension-dev-guide/configuration/sensitive-and-environment-settings.html#sensitive-values
• https://devdocs.magento.com/guides/v2.3/extension-dev-guide/configuration/sensitive-and-environment-settings.html#sensitive-values
• https://devdocs.magento.com/guides/v2.4/graphql/mutations/update-customer.html
• https://devdocs.magento.com/guides/v2.4/graphql/mutations/create-customer.html
• https://devdocs.magento.com/guides/v2.4/graphql/mutations/create-customer-v2.html
• https://devdocs.magento.com/guides/v2.4/graphql/mutations/update-customer-v2.html
• https://devdocs.magento.com/guides/v2.4/graphql/mutations/change-customer-password.html
• https://devdocs.magento.com/guides/v2.4/graphql/mutations/update-customer-email.html
• https://devdocs.magento.com/guides/v2.4/graphql/queries/customer.html
• https://devdocs.magento.com/guides/v2.4/graphql/develop/resolvers.html

whatsnew
Added a legal disclaimer to references of the date_of_birth attribute of the customer database entity.

[jeff-matthews]

running tests

[ghost]

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