Update the msbuild version to 17.4.8

Remove the conditional
Update the nuget.config entry for the new build

Author: marcpopMSFT

NuGet.config

@@ -37,7 +37,7 @@
     <add key="dotnet-libraries" value="https://pkgs.dev.azure.com/dnceng/public/_packaging/dotnet-libraries/nuget/v3/index.json" />
     <add key="dotnet-libraries-transport" value="https://pkgs.dev.azure.com/dnceng/public/_packaging/dotnet-libraries-transport/nuget/v3/index.json" />
     <add key="vs-impl" value="https://pkgs.dev.azure.com/azure-public/vside/_packaging/vs-impl/nuget/v3/index.json" />
-    <add key="msbuild" value="https://pkgs.dev.azure.com/dnceng/public/_packaging/darc-pub-DotNet-msbuild-Trusted-020b625c/nuget/v3/index.json" />
+    <add key="darc-pub-DotNet-msbuild-Trusted-6918b86" value="https://pkgs.dev.azure.com/dnceng/public/_packaging/darc-pub-DotNet-msbuild-Trusted-6918b863/nuget/v3/index.json" />   <!-- Used for Rich Navigation indexing task -->
     <!-- Used for Rich Navigation indexing task -->
     <add key="richnav" value="https://pkgs.dev.azure.com/azure-public/vside/_packaging/vs-buildservices/nuget/v3/index.json" />
   </packageSources>

eng/Versions.props

@@ -114,7 +114,7 @@
           so target one that matches the version in minimumMSBuildVersion.
 
           This avoids the need to juggle references to packages that have been updated in newer MSBuild. -->
-    <MicrosoftBuildPackageVersion Condition="exists('$(RepoRoot)\src\Layout\redist\minimumMSBuildVersion') and '$(DotNetBuildFromSource)' != 'true'">17.4.6</MicrosoftBuildPackageVersion>
+    <MicrosoftBuildPackageVersion Condition="'$(DotNetBuildFromSource)' != 'true'">17.4.8</MicrosoftBuildPackageVersion>
     <MicrosoftBuildFrameworkPackageVersion>$(MicrosoftBuildPackageVersion)</MicrosoftBuildFrameworkPackageVersion>
     <MicrosoftBuildRuntimePackageVersion>$(MicrosoftBuildPackageVersion)</MicrosoftBuildRuntimePackageVersion>
     <MicrosoftBuildLocalizationPackageVersion>17.7.4-preview-23476-01</MicrosoftBuildLocalizationPackageVersion>