This is probably going to come off a bit rant-y, but please trust me when I say this isn't directed exclusively at this post. For more examples from the last week alone (and why I think this needs to be addressed on a larger scale), see here, here, here, here, and here.

So, for the specific question, no, this is not generally a punishment for apostasy known to be used either in canonical statutes or by local custom. Moreover, crucifixion was outlawed by Emperor Constantine and was not used as a form of punishment afterwards. Of course, I cannot definitively state that it was never used because I am not omniscient, but it has no precedent that I know of.

More generally:

It's a television show. It's a fictional show put on television for the purpose of entertainment. A member of the production team had this too say about it:

...we want people to watch it. A historical account of the Vikings would reach hundreds, occasionally thousands, of people. Here we’ve got to reach millions.

Asking about the historical accuracy of Vikings is like asking about the historical accuracy of Game of Thrones or Attack on Titan, or shudder 300. It doesn't even have the basic historical grounding of real persons and events that made shows like Rome, The Borgias, and The Tudors vaguely connected with something which might be considered (loosely) a historical reality.

If you have a question about the historical accuracy of a TV drama, the answer is, almost universally, going to be 'no.' Even for a show which tries really hard, like HBO's Rome, is still going to only get "The broad outlines are ok and it really captured the spirit of the time" from trained historians.

So, please, consider the question and its context before you ask it. Or, better yet, if it's not a part of an actual documentary, assume it's not an accurate reflection of the past.