Teams who is more common in the last few decades, but either is acceptable. To answer this, I'll use an American corpus, a British corpus, and a web-based corpus.
Corpus of Contemporary American English (1990-2019):
- teams who: 201 results
- teams which: 19 results
British National Corpus (1980s-1993):
- teams who: 63 results
- teams which: 28 results
News on the Web (2010s):
- teams who: 15,242 results
- teams which: 3,430 results
In all contexts, teams who shows up more often than teams which.
More generally, teams is an example of a collective noun which can refer to either the entity as a whole or to the individual people involved. Generally, traditionalists teach that which should be used for entities but who should be used for people. Meanwhile, in the context of collective nouns, advice-givers on usage treat who and which as a matter of emphasis - use who when emphasizing the people on teams, and which when emphasizing the teams as units (see e.g. Tanya Trusler at ESL Library or English Plus Language Blog).
In other words, both can be correct, who is more common, and if you can't decide, think about whether you would rather emphasize the people or the unit.