Fidelity’s Blue Chip Growth Fund raised the value of its position in Elon Musk’s X by 4.4% in April.Fidelity, which gained its stake by helping Musk complete his $44 billion purchase of what was then known as Twitter, valued its position at $5.51 million as of April 30, according to a report released Thursday. That was up from $5.28 million at the end of March....