@Rob DeMartin/Netflix Netflix has dropped a new teaser trailer for “Sly,” which chronicles Sylvester Stallone’s highs and lows of his near 50-year Hollywood career. “Sly” is directed by Thom Zimny (“Springsteen on Broadway”) and produced by Sean Stuart. The 40-second clip doesn’t give much away about the content of the documentary. But in the first-look clip, Stallone…