Merged PR 51052: [internal/release/8.0.3xx] Updated NuGet.config - replace msbuild feed bb7

Updated NuGet.config - replace msbuild feed bb7

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#### AI description  (iteration 1)
#### PR Classification
Configuration update.

#### PR Summary
This pull request updates the NuGet configuration to replace the msbuild feed with a new package source.
- `NuGet.config`: Added a package source entry with key "darc-pub-DotNet-msbuild-Trusted-bb7294f-1" pointing to a new NuGet feed.
<!-- GitOpsUserAgent=GitOps.Apps.Server.pullrequestcopilot -->

Author: vseanreesermsft

NuGet.config

@@ -13,6 +13,7 @@
     <add key="darc-int-dotnet-aspnetcore-cea5fa6" value="https://pkgs.dev.azure.com/dnceng/internal/_packaging/darc-int-dotnet-aspnetcore-cea5fa61/nuget/v3/index.json" />
     <!--  End: Package sources from dotnet-aspnetcore -->
     <!--  Begin: Package sources from DotNet-msbuild-Trusted -->
+    <add key="darc-pub-DotNet-msbuild-Trusted-bb7294f-1" value="https://pkgs.dev.azure.com/dnceng/public/_packaging/darc-pub-DotNet-msbuild-Trusted-bb7294f7-1/nuget/v3/index.json" />
     <!--  End: Package sources from DotNet-msbuild-Trusted -->
     <!--  Begin: Package sources from dotnet-roslyn-analyzers -->
     <!--  End: Package sources from dotnet-roslyn-analyzers -->
@@ -53,6 +54,7 @@
     <add key="darc-int-dotnet-aspnetcore-cea5fa6" value="true" />
     <!--  End: Package sources from dotnet-aspnetcore -->
     <!--  Begin: Package sources from DotNet-msbuild-Trusted -->
+    <add key="darc-pub-DotNet-msbuild-Trusted-bb7294f-1" value="true" />
     <!--  End: Package sources from DotNet-msbuild-Trusted -->
     <!--  Begin: Package sources from dotnet-emsdk -->
     <!--  End: Package sources from dotnet-emsdk -->