feat: Remove unused AttendanceStatus enum

- Remove the `AttendanceStatus` enum from the `calendar` module.

heromodels/src/models/calendar/rhai.rs

@@ -1,7 +1,7 @@
 use rhai::{Engine, EvalAltResult, ImmutableString, NativeCallContext};
 use std::sync::Arc;
 
-use super::calendar::{AttendanceStatus, Attendee, Calendar, Event};
+use super::calendar::{Attendee, Calendar, Event};
 use crate::db::hero::OurDB;
 use adapter_macros::rhai_timestamp_helpers;
 use adapter_macros::{adapt_rhai_i64_input_fn, adapt_rhai_i64_input_method};