dotnet-svcutil: add reference to wcf 6.* for net7.0 target project. (#5465)

Author: imcarolwang

src/dotnet-svcutil/lib/src/Shared/TargetFrameworkHelper.cs

@@ -74,6 +74,15 @@ internal class TargetFrameworkHelper
                 ProjectDependency.FromPackage("System.ServiceModel.UnixDomainSocket", "6.2.*"),
                 ProjectDependency.FromPackage("System.Web.Services.Description", "6.2.*")
             } },
+            {new Version("7.0"), new List<ProjectDependency> {
+                ProjectDependency.FromPackage("System.ServiceModel.Http", "6.2.*"),
+                ProjectDependency.FromPackage("System.ServiceModel.NetTcp", "6.2.*"),
+                ProjectDependency.FromPackage("System.ServiceModel.NetNamedPipe", "6.2.*"),
+                ProjectDependency.FromPackage("System.ServiceModel.Primitives", "6.2.*"),
+                ProjectDependency.FromPackage("System.ServiceModel.Federation", "6.2.*"),
+                ProjectDependency.FromPackage("System.ServiceModel.UnixDomainSocket", "6.2.*"),
+                ProjectDependency.FromPackage("System.Web.Services.Description", "6.2.*")
+            } },
             {new Version("8.0"), new List<ProjectDependency> {
                 ProjectDependency.FromPackage("System.ServiceModel.Http", "8.*"),
                 ProjectDependency.FromPackage("System.ServiceModel.NetTcp", "8.*"),