Everywhere: Switch from (void) to [[maybe_unused]] (#4473)

Problem:
- `(void)` simply casts the expression to void. This is understood to
  indicate that it is ignored, but this is really a compiler trick to
  get the compiler to not generate a warning.

Solution:
- Use the `[[maybe_unused]]` attribute to indicate the value is unused.

Note:
- Functions taking a `(void)` argument list have also been changed to
  `()` because this is not needed and shows up in the same grep
  command.

Libraries/LibWeb/Bindings/WindowObject.cpp

@@ -337,7 +337,6 @@ JS_DEFINE_NATIVE_GETTER(WindowObject::document_getter)
 JS_DEFINE_NATIVE_SETTER(WindowObject::document_setter)
 {
     // FIXME: Figure out what we should do here. Just ignore attempts to set window.document for now.
-    UNUSED_PARAM(value);
 }
 
 JS_DEFINE_NATIVE_GETTER(WindowObject::performance_getter)