Revert "Use a private pythia8 200pre1 tarball in cmsdist 73x with some o...

Reverts cms-sw/cmsdist#1028

I missed it the first time but this PR actually breaks evtgen which requires to update its use of pythia API.
Example error:

```
EvtGenExternal/EvtPythiaEngine.cpp:240:40: error: 'class Pythia8::Event' has no member named 'daughterList'
std::vector<int> daugList = theEvent.daughterList(startInt);
```