Unfortunately there's no built in way in Hype to do this.
Super easy in Automator though!
remove hyperesources.zip (86.0 KB)
Once you do that, you can use a standard text editor to do a find/replace and remove instances of
.hyperesources with whatever you choose to replace that string with.
If you don't have a text editor that supports this, I recommend Atom. Open Atom, drag a parent folder containing all your .html files onto it, and then type ⌘ + shift + f to do a global 'find' in your project. Next, type .hyperesources in the find field and insert hyperesources into the 'replace in project' field.