Use M.NC.App RefPack version for dotnet targeting pack dependency version

[wtgodbe]

We should keep the dependency on the dotnet-targeting-pack in line with our (pinned) dependency on `Microsoft.NetCore.App.Ref. This fixes the following error in Core-SDK:

EXEC : error : Failed dependencies: [/home/vsts/work/1/s/src/redist/redist.csproj]
##[error]EXEC(0,0): error : Failed dependencies:
dotnet-targeting-pack-3.0 >= 3.0.1 is needed by aspnetcore-targeting-pack-3.0-3.0.1-1.x86_64

/home/vsts/work/1/s/src/redist/targets/GenerateRPMs.targets(295,5): error MSB3073: The command "sudo rpm -iv /home/vsts/work/1/s/artifacts/obj/redist/Release/downloads/aspnetcore-targeting-pack-3.0.1.rpm" exited with code 1. [/home/vsts/work/1/s/src/redist/redist.csproj]

##[error]src/redist/targets/GenerateRPMs.targets(295,5): error MSB3073: The command "sudo rpm -iv /home/vsts/work/1/s/artifacts/obj/redist/Release/downloads/aspnetcore-targeting-pack-3.0.1.rpm" exited with code 1.

CC @dougbu @JunTaoLuo @nguerrera @mmitche