Fix SetupProcess project's target framework

The project was hard coded to target .NET 4.7.2 instead of using
the TargetFramework.props file. This was preventing it being
referenced by the UnitTests project.

Mono.Addins.SetupProcess/Mono.Addins.SetupProcess.csproj

@@ -1,5 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
 <Project DefaultTargets="Build" ToolsVersion="4.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <Import Project="..\TargetFrameworks.props" />
   <PropertyGroup>
     <Configuration Condition=" '$(Configuration)' == '' ">Debug</Configuration>
     <Platform Condition=" '$(Platform)' == '' ">AnyCPU</Platform>
@@ -11,7 +12,6 @@
     <AssemblyName>Mono.Addins.SetupProcess</AssemblyName>
     <SignAssembly>True</SignAssembly>
     <AssemblyOriginatorKeyFile>..\mono-addins.snk</AssemblyOriginatorKeyFile>
-    <TargetFrameworkVersion>v4.7.2</TargetFrameworkVersion>
   </PropertyGroup>
   <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|AnyCPU' ">
     <DebugSymbols>true</DebugSymbols>