Update nuspec on .net 6.0 (#2317)

Author: ErikEJ

tools/specs/Microsoft.Data.SqlClient.nuspec

@@ -57,6 +57,7 @@ When using NuGet 3.x this package requires at least version 3.4.</description>
         <dependency id="Microsoft.IdentityModel.JsonWebTokens" version="6.35.0" />
         <dependency id="Microsoft.SqlServer.Server" version="1.0.0"/>
         <dependency id="System.Configuration.ConfigurationManager" version="6.0.1" exclude="Compile" />
+        <dependency id="System.Diagnostics.DiagnosticSource" version="6.0.1" exclude="Compile" />
         <dependency id="System.Runtime.Caching" version="6.0.0" exclude="Compile" />
       </group>
       <group targetFramework="netstandard2.0">