Remove stale dependencies from SqlClient

The System.Security.Cryptography.Cng and System.Security.Principal.Windows packages don't ship anymore since .NET 5 and are provided by the .NETCoreApp framework implicitly.

Removing dependencies to those for .NETCoreApp TFMs to stop bringing these older versions in transitively.

Fixes dotnet/runtime#93577

tools/specs/Microsoft.Data.SqlClient.nuspec

@@ -50,8 +50,6 @@ When using NuGet 3.x this package requires at least version 3.4.</description>
         <dependency id="System.Runtime.Caching" version="6.0.0" exclude="Compile" />
         <dependency id="System.Text.Encoding.CodePages" version="6.0.0" exclude="Compile" />
         <dependency id="System.Text.Encodings.Web" version="6.0.0" />
-        <dependency id="System.Security.Cryptography.Cng" version="5.0.0" />
-        <dependency id="System.Security.Principal.Windows" version="5.0.0" exclude="Compile" />
       </group>
       <group targetFramework="net6.0">
         <dependency id="Microsoft.Data.SqlClient.SNI.runtime" version="5.1.1" exclude="Compile" />
@@ -64,8 +62,6 @@ When using NuGet 3.x this package requires at least version 3.4.</description>
         <dependency id="System.Runtime.Caching" version="6.0.0" exclude="Compile" />
         <dependency id="System.Text.Encoding.CodePages" version="6.0.0" exclude="Compile" />
         <dependency id="System.Text.Encodings.Web" version="6.0.0" />
-        <dependency id="System.Security.Cryptography.Cng" version="5.0.0" />
-        <dependency id="System.Security.Principal.Windows" version="5.0.0" exclude="Compile" />
       </group>
       <group targetFramework="netstandard2.0">
         <dependency id="Microsoft.Data.SqlClient.SNI.runtime" version="5.1.1" exclude="Compile" />