Update target frameworks of test and benchmark projects (#420)

* Build(deps): Update target framework of test project to net9.0 and bump package versions

* Build(deps): Update target framework of benchmark project to net9.0 and upgrade BenchmarkDotNet to version 0.14.0

PreMailer.Net/Benchmarks/Benchmarks.csproj

@@ -2,12 +2,12 @@
 
   <PropertyGroup>
     <OutputType>Exe</OutputType>
-	<TargetFramework>net7.0</TargetFramework>
+	<TargetFramework>net9.0</TargetFramework>
     <Nullable>enable</Nullable>
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="BenchmarkDotNet" Version="0.13.3" />
+    <PackageReference Include="BenchmarkDotNet" Version="0.14.0" />
   </ItemGroup>
 
   <ItemGroup>

PreMailer.Net/PreMailer.Net.Tests/PreMailer.Net.Tests.csproj

@@ -1,17 +1,17 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>net7.0</TargetFramework>
+    <TargetFramework>net9.0</TargetFramework>
 
     <IsPackable>false</IsPackable>
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.9.0" />
-    <PackageReference Include="Moq" Version="4.20.70" />
-    <PackageReference Include="xunit" Version="2.7.0" />
-    <PackageReference Include="xunit.runner.visualstudio" Version="2.5.7" />
-    <PackageReference Include="coverlet.collector" Version="6.0.2" />
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.12.0" />
+    <PackageReference Include="Moq" Version="4.20.72" />
+    <PackageReference Include="xunit" Version="2.9.3" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="3.0.1" />
+    <PackageReference Include="coverlet.collector" Version="6.0.4" />
   </ItemGroup>
 
   <ItemGroup>