Remove net6.0 build, replace by 8.0 #861

	name: CI

	on: [push, pull_request, workflow_dispatch]

	env:
	DOTNET_CLI_TELEMETRY_OPTOUT: 'true'
	# A workflow run is made up of one or more jobs that can run sequentially or in parallel
	jobs:
	net60:
	name: '8.0'
	runs-on: ubuntu-latest
	steps:
	- uses: actions/checkout@v2
	- uses: actions/setup-dotnet@v1
	with:
	dotnet-version: '8.0.x'
	- run: ./Build/CI/tests.sh
	env:
	BUILD_ARGS: /p:AdditionalDefineConstants=SECP256K1_VERIFY
	Framework: net8.0
	dotnetcore60standard20:
	name: '8.0 with netstandard2.0'
	runs-on: ubuntu-latest
	steps:
	- uses: actions/checkout@v2
	- uses: actions/setup-dotnet@v1
	with:
	dotnet-version: '8.0.x'
	- run: ./Build/CI/tests.sh
	env:
	BUILD_ARGS: /p:TargetFrameworkOverride=netstandard2.0
	Framework: net8.0
	dotnetcore60macos:
	name: '8.0 on Mac-OS'
	runs-on: macOS-latest
	steps:
	- uses: actions/checkout@v2
	- uses: actions/setup-dotnet@v1
	with:
	dotnet-version: '8.0.x'
	- run: ./Build/CI/tests.sh
	env:
	Framework: net8.0
	dotnetcore60winfx:
	name: '8.0 on Windows NetFramework472'
	runs-on: windows-latest
	steps:
	- uses: actions/checkout@v2
	- uses: actions/setup-dotnet@v1
	with:
	dotnet-version: '8.0.x'
	- run: dotnet clean -c Release ./NBitcoin.Tests/NBitcoin.Tests.csproj && dotnet nuget locals all --clear
	- run: dotnet test -c Release -v n ./NBitcoin.Tests/NBitcoin.Tests.csproj --filter "RestClient=RestClient\|RPCClient=RPCClient\|Protocol=Protocol\|Core=Core\|UnitTest=UnitTest\|Altcoins=Altcoins\|PropertyTest=PropertyTest" -p:ParallelizeTestCollections=false -f net472

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