The sports collectibles market is hot — again. NFL tight end Rob Gronkowski recently auctioned off a set of five trading cards valued at more than $1.6 million, including one card that sold for a reported $435,000. While high, the values weren’t top-of-the-collectibles-market high — the most expensive card sold recently was a rare, mint condition, signed, Patrick Mahomes rookie card that sold at auction for a record $861,000 in January, just days before the Kansas City Chiefs quarterback lost to Gronk’s Tampa Bay …