Update Drupal Core to v9.3.15 (9.x)

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change
drupal/core-dev-pinned	require-dev	patch	9.3.14 -> 9.3.15
drupal/core-project-message (source)	require	patch	9.3.14 -> 9.3.15
drupal/core-recommended	require	patch	9.3.14 -> 9.3.15

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Release Notes

drupal/core-dev-pinned

### [`v9.3.15`](https://togithub.com/drupal/core-dev-pinned/compare/9.3.14...9.3.15) [Compare Source](https://togithub.com/drupal/core-dev-pinned/compare/9.3.14...9.3.15)

drupal/core-project-message

### [`v9.3.15`](https://togithub.com/drupal/core-project-message/compare/9.3.14...9.3.15) [Compare Source](https://togithub.com/drupal/core-project-message/compare/9.3.14...9.3.15)

drupal/core-recommended

### [`v9.3.15`](https://togithub.com/drupal/core-recommended/compare/9.3.14...9.3.15) [Compare Source](https://togithub.com/drupal/core-recommended/compare/9.3.14...9.3.15)

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