chore: bump from .net 6 to .net 8

Author: JamieMagee

src/Directory.Build.props

@@ -3,6 +3,7 @@
   <Import Project="$([MSBuild]::GetPathOfFileAbove('Directory.Build.props', '$(MSBuildThisFileDirectory)../'))"/>
 
   <PropertyGroup Label="Build">
+    <TargetFramework>net8.0</TargetFramework>
     <GenerateDocumentationFile>true</GenerateDocumentationFile>
     <SymbolPackageFormat>snupkg</SymbolPackageFormat>
     <SuppressTfmSupportBuildWarnings>true</SuppressTfmSupportBuildWarnings>

src/Octokit.Webhooks.AspNetCore/Octokit.Webhooks.AspNetCore.csproj

@@ -1,9 +1,5 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
-  <PropertyGroup Label="Build">
-    <TargetFramework>net6.0</TargetFramework>
-  </PropertyGroup>
-
   <PropertyGroup Label="Package">
     <Product>Octokit.Webhooks.AspNetCore</Product>
     <Description>GitHub webhook events toolset for .NET</Description>

src/Octokit.Webhooks.AzureFunctions/Octokit.Webhooks.AzureFunctions.csproj

@@ -1,9 +1,5 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
-  <PropertyGroup>
-    <TargetFramework>net6.0</TargetFramework>
-  </PropertyGroup>
-
   <PropertyGroup Label="Package">
     <Product>Octokit.Webhooks.AzureFunctions</Product>
     <Description>GitHub webhook events toolset for Azure Functions</Description>

src/Octokit.Webhooks/Octokit.Webhooks.csproj

@@ -1,9 +1,5 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
-  <PropertyGroup Label="Build">
-    <TargetFramework>net6.0</TargetFramework>
-  </PropertyGroup>
-
   <PropertyGroup Label="Package">
     <Product>Octokit.Webhooks</Product>
     <Description>GitHub webhook events definitions for .NET</Description>