Docs: Resolve inconsistency regarding Windows Server 2025 support
## **Description** There is an inconsistency in the documentation regarding support for Windows Server 2025. The [Docker executor supported Windows versions](https://docs.gitlab.com/runner/executors/docker/#supported-windows-versions) page does not list Windows 2025, but the [Windows version support policy](https://docs.gitlab.com/runner/install/support-policy/#windows-version-support) indicates that it is supported. Looking at !5170 (merged), it is clear that Windows 2025 is indeed supported, so the docs should reflect this as well.
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