[Issue] System configuration Validation

[m2-assistant]

This issue is automatically created based on existing pull request: #29486: System configuration Validation

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Description (*)

This field should be save empty, but incorrect validation was applied. Because of that, admin user couldn't save the empty value.

Preconditions:

1. Base Magento 2.4-develop installed.

Steps to reproduce:

1. Log in in the admin area.
2. Go to Stores -> Configurations -> Services -> OAuth -> Access Token Expiration.
3. Empty 'Customer Token Lifetime (hours)' field and save config.
4. Empty 'Admin Token Lifetime (hours)' field and save config.

Expected result:

Config saved successfully.

Actual result:

Config is not saved. Incorrect validation applied.

Contribution checklist (*)

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All automated tests passed successfully (all builds are green)
• All new or changed code is covered with unit/integration tests (if applicable)

[magento-engcom-team]

@engcom-Oscar Thank you for verifying the issue.

Unfortunately, not enough information was provided to acknowledge ticket. Please consider adding the following:

• Add "Reproduced on " label(s) to this ticket based on verification result

Once all required information is added, please add label "Issue: Confirmed" again.
Thanks!