Smart ring maker Oura Health Oy is getting a $75 million investment from medical device firm Dexcom Inc., setting the stage for the two companies to share data and cross-sell products.Dexcom is investing the money as part of a Series D financing round, valuing Oura at more than $5 billion, according to a statement Tuesday. That’s up from a $2.6 billion valuation in the ring maker’s Series C round in 2022....