[cli] Update target frameworks to target both .NET 6.0 and 8.0 (#130)

* Bump dotnet SDK 8.0.300 in global.json

* Update target frameworks to target both `.NET 6.0` and `.NET 8.0`

global.json

@@ -1,6 +1,6 @@
 {
   "sdk": {
-    "version": "6.0.400",
+    "version": "8.0.300",
     "allowPrerelease": false,
     "rollForward": "latestFeature"
   }

src/Dax.Vpax.CLI/Dax.Vpax.CLI.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>net6.0</TargetFramework>
+    <TargetFrameworks>net6.0;net8.0</TargetFrameworks>
     <OutputType>Exe</OutputType>
     <Nullable>enable</Nullable>
     <LangVersion>10.0</LangVersion>
@@ -31,7 +31,6 @@
     <PackageReference Include="Dax.Vpax" Version="1.6.0" />
     <PackageReference Include="System.CommandLine" Version="2.0.0-beta4.22272.1" />
     <PackageReference Include="Nerdbank.GitVersioning" Version="3.6.133" PrivateAssets="all" />
-    <PackageReference Include="Microsoft.SourceLink.GitHub" Version="1.1.1" PrivateAssets="all" />
   </ItemGroup>
 
   <ItemGroup>