feat: bump openapi to 5.3.0

[NickUfer]

This PR bumps openapi-generator to version 5.3.0, which includes a fix for the php client sdk generator.

Related Issue or Design Document

Generator fix: OpenAPITools/openapi-generator#10576
Indirectly fixes ory/kratos-client-php#3 when the sdk is regenerated

Checklist

• I have read the contributing guidelines
  and signed the CLA.
• I have referenced an issue containing the design document if my change
  introduces a new feature.
• I have read the security policy.
• I confirm that this pull request does not address a security
  vulnerability. If this pull request addresses a security vulnerability, I
  confirm that I got green light (please contact
  security@ory.sh) from the maintainers to push
  the changes.
• I have added tests that prove my fix is effective or that my feature
  works.
• I have added necessary documentation within the code base (if
  appropriate).

Further comments

[aeneasr]

🙏