Drop STS .net7 for LTS .net8

Author: kzu

src/Ulid.Cli/Ulid.Cli.csproj

@@ -12,7 +12,7 @@
 
     <PropertyGroup>
         <OutputType>Exe</OutputType>
-        <TargetFrameworks>net6.0;net7.0</TargetFrameworks>
+        <TargetFrameworks>net6.0;net8.0</TargetFrameworks>
         <ToolCommandName>dotnet-ulid</ToolCommandName>
         <PackAsTool>true</PackAsTool>
         <LangVersion>7.3</LangVersion>