docs: Update repo markdown to reflect supported frameworks

Author: amanda-tarafa

CONTRIBUTING.md

@@ -40,7 +40,7 @@ These libraries are split into:
 
 ## Building and .NET Core
 
-We use Visual Studio 2017 to edit the Support Libraries.
+We use Visual Studio 2022 to edit the Support Libraries.
 
 We use [dotnet cli][dotnetcli] for testing and building both the generated Client Libraries and the Support Libraries.
 

Frameworks.md

@@ -2,7 +2,7 @@
 
 This isn't quite a simple as it could be, but it's fairly simple:
 
-1. Use a Windows machine with `Visual Studio 2017 v15.4` or greater; and a recent version of `git`.
+1. Use a Windows machine with `Visual Studio 2022 v17.8` or greater; and a recent version of `git`.
 1. `git clone https://github.com/google/google-api-dotnet-client.git`
 1. Delete all files from the `DiscoveryJson` directory. They are all `.json` files.
 1. Copy the discovery-doc `json` file into the `DiscoveryJson` directory.

HowToGenerateAPackage.md

@@ -7,14 +7,6 @@
 
 _If you're working with **Google Cloud Platform** APIs such as Datastore or Pub/Sub, consider using the [Cloud Client Libraries for .NET instead](https://github.com/googleapis/google-cloud-dotnet). These are the new and idiomatic .NET libraries targeted specifically at Google Cloud Platform Services._
 
-# Announcement: plan for changing library targets
-
-We are planning to change the set of target frameworks supported
-by the packages generated from this repository. Please see the
-[announcement
-issue](https://github.com/googleapis/google-api-dotnet-client/issues/2561)
-for more details and to provide feedback.
-
 # Library Maintenance
 
 This client library is supported but in maintenance mode only. We are fixing necessary bugs and adding essential features to ensure this library continues to meet your needs for accessing Google APIs. Non-critical issues will be closed. Any issue may be reopened if it is causing ongoing problems.
@@ -30,13 +22,9 @@ Please see the [help page](https://cloud.google.com/dotnet/docs/reference/help/r
 
 ## Supported Frameworks
 
-(Note: this set may change in early 2024, as per
-[this announcement
-issue](https://github.com/googleapis/google-api-dotnet-client/issues/2561).
-
-* .NET Framework 4.5+
-* netstandard1.3, providing .NET Core support
-* netstandard2.0, providing [ASP.NET Core Support](https://www.nuget.org/packages/Google.Apis.Auth.AspNetCore)
+* .NET Framework 4.6.2+
+* .NET Standard 2.0
+* .NET 6.0+
 
 ## Unsupported Frameworks
 
@@ -45,8 +33,6 @@ issue](https://github.com/googleapis/google-api-dotnet-client/issues/2561).
 * Xamarin
 * Unity
 
-For more details on framework support see [Frameworks.md](Frameworks.md).
-
 See the [FAQ](FAQ.md#why-arent-unity-xamarin-or-uwp-supported) for details regarding the lack of UWP, Xamarin, and Unity support.
 
 Note that [Firebase](https://firebase.google.com/) is available on Unity, and focuses on the need of this platform.