Update the VS warning to point to 18.0

Author: marcpopMSFT

src/Tasks/Microsoft.NET.Build.Tasks/targets/Microsoft.NET.SupportedTargetFrameworks.props

@@ -33,7 +33,7 @@ Copyright (c) .NET Foundation. All rights reserved.
     <PropertyGroup>
         <!-- This is for a better error experience when using an older VS (with an older SDK) to target a newer TFM. The value should be the min VS version for N+1 version-->
         <UnsupportedTargetFrameworkVersion>10.0</UnsupportedTargetFrameworkVersion>
-        <MinimumVisualStudioVersionForUnsupportedTargetFrameworkVersion>17.16</MinimumVisualStudioVersionForUnsupportedTargetFrameworkVersion>
+        <MinimumVisualStudioVersionForUnsupportedTargetFrameworkVersion>18.0</MinimumVisualStudioVersionForUnsupportedTargetFrameworkVersion>
     </PropertyGroup>
 
     <!-- .NET Standard -->