Remove reference to .NET 9 'Preview' in the EF9 targeting sentence as…

… .NET9 is now GA (#4880)

Remove reference to .NET 9 'Preview' in the EF9 targeting sentence as .NET9 is now GA

entity-framework/core/what-is-new/ef-core-9.0/whatsnew.md

@@ -15,7 +15,7 @@ EF9 is available as [daily builds](https://github.com/dotnet/efcore/blob/main/do
 > [!TIP]
 > You can run and debug into the samples by [downloading the sample code from GitHub](https://github.com/dotnet/EntityFramework.Docs). Each section below links to the source code specific to that section.
 
-EF9 targets .NET 8, and can therefore be used with either [.NET 8 (LTS)](https://dotnet.microsoft.com/download/dotnet/8.0) or a [.NET 9 preview](https://dotnet.microsoft.com/download/dotnet/9.0).
+EF9 targets .NET 8, and can therefore be used with either [.NET 8 (LTS)](https://dotnet.microsoft.com/download/dotnet/8.0) or [.NET 9](https://dotnet.microsoft.com/download/dotnet/9.0).
 
 > [!TIP]
 > The _What's New_ docs are updated for each preview. All the samples are set up to use the [EF9 daily builds](https://github.com/dotnet/efcore/blob/main/docs/DailyBuilds.md), which usually have several additional weeks of completed work compared to the latest preview. We strongly encourage use of the daily builds when testing new features so that you're not doing your testing against stale bits.