Clover Health, an insurance startup using data science for preventative health care, has become Silicon Valley’s newest, and a rather reluctant, unicorn. Alphabet Inc.’s venture arm GV and other investors have put $130 million into the San Francisco-based company, valuing it at $1.2 billion, according to people familiar with the matter. Startups worth more than $1 billion on paper are known as unicorns. The funding round closed Wednesday.