Post-hardcore/emo group Hawthorne Heights is set to play Underbelly on Friday. And if you feel like that sentence reads as though it was copied-and-pasted from a different year, you’re not alone. To clear things up: yes, emo is thriving in 2021. And, yes, Underbelly, the much-beloved but short-lived Downtown Jacksonville music venue is back.  Along with Burro Bar and Club …