docs: Prepare release of v0.25.1.

Author: seifertm

docs/reference/changelog.rst

@@ -2,7 +2,7 @@
 Changelog
 =========
 
-0.25.1 (UNRELEASED)
+0.25.1 (2025-01-02)
 ===================
 - Fixes an issue that caused a broken event loop when a function-scoped test was executed in between two tests with wider loop scope `#950 <https://github.com/pytest-dev/pytest-asyncio/issues/950>`_
 - Improves test collection speed in auto mode `#1020 <https://github.com/pytest-dev/pytest-asyncio/pull/1020>`_