chore: update .net version

Ragon.Server.ENetServer/Ragon.Server.ENetServer.csproj

@@ -4,7 +4,6 @@
         <ImplicitUsings>enable</ImplicitUsings>
         <Nullable>enable</Nullable>
         <RootNamespace>Ragon.ENet</RootNamespace>
-        <TargetFrameworks>net6.0;net7.0;net8.0</TargetFrameworks>
         <GeneratePackageOnBuild>true</GeneratePackageOnBuild>
         <Copyright>Eduard Kargin</Copyright>
         <Authors>Eduard Kargin</Authors>
@@ -15,6 +14,7 @@
         <PackageLicenseExpression>Apache-2.0</PackageLicenseExpression>
         <RepositoryUrl>https://github.com/edmand46/Ragon</RepositoryUrl>
         <RepositoryType>Source</RepositoryType>
+        <TargetFramework>net9.0</TargetFramework>
     </PropertyGroup>
 
     <ItemGroup>

Ragon.Server.WebSocketServer/Ragon.Server.WebSocketServer.csproj

@@ -4,7 +4,6 @@
         <ImplicitUsings>enable</ImplicitUsings>
         <Nullable>enable</Nullable>
         <RootNamespace>Ragon.WebSockets</RootNamespace>
-        <TargetFrameworks>net6.0;net7.0;net8.0</TargetFrameworks>
         <Copyright>Eduard Kargin</Copyright>
         <Authors>Eduard Kargin</Authors>
         <GeneratePackageOnBuild>true</GeneratePackageOnBuild>
@@ -15,6 +14,7 @@
         <PackageLicenseExpression>Apache-2.0</PackageLicenseExpression>
         <RepositoryUrl>https://github.com/edmand46/Ragon</RepositoryUrl>
         <RepositoryType>Source</RepositoryType>
+        <TargetFramework>net9.0</TargetFramework>
     </PropertyGroup>
 
     <ItemGroup>

Ragon.Server/Ragon.Server.csproj

@@ -14,7 +14,7 @@
         <RepositoryUrl>https://github.com/edmand46/Ragon</RepositoryUrl>
         <RepositoryType>Source</RepositoryType>
         <LangVersion>10</LangVersion>
-        <TargetFrameworks>net6.0;net7.0;net8.0</TargetFrameworks>
+        <TargetFramework>net9.0</TargetFramework>
     </PropertyGroup>
 
     <ItemGroup>