Good conversation on the topic here
Basically, it is becoming more common in English writing to use the masculine “hero” as gender neutral when the figure is a famous and/or historical figure.
If it is a fictional character, “heroine” is still widely used.
There’s been a wider trend of using gender neutral terms in the language. “They” as a replacement for “he” or “she”, for example, used to be improper but is now quite widely accepted and not only when speaking about a non-binary person.
Take that one up with my English professors in University.