Get rid of the "sync" command about pixi

[ruben-arts]

I think it would be nice if px without commands would do a "sync" but that it also does the sync on run, add, build, test etc.

[baszalmstra]

Can you explain why you want that?

[ruben-arts]

Yes, it's about the ergonomics of the tool. Only having add and run to trigger the installation forces the user to run those to test the installation. In my case, I was having solving issues and I had to use px run to debug what the problem was.
In the perfect world, it wouldn't be needed as all the px runs would work. But I think it would be nice to keep some kind of "render env" step.

Next to that, I was getting errors because it was trying to run something which was not there as it expected input. This is not the issue as it could be fixed but it shows that me as a user didn't want the tool to be touching any of that run code as it was not needed at all.

[baszalmstra]

Fixed by #25

If we want the behavior @ruben-arts describes then let's add another issue for that.