Remove unnecessary async_trait usages

crates/caldav/src/principal/mod.rs

@@ -64,7 +64,6 @@ pub enum PrincipalPropName {
     CalendarUserAddressSet,
 }
 
-#[async_trait(?Send)]
 impl Resource for PrincipalFile {
     type PropName = PrincipalPropName;
     type Prop = PrincipalProp;

crates/dav/src/resource.rs

@@ -10,7 +10,6 @@ use serde::{Deserialize, Serialize};
 use std::str::FromStr;
 use strum::VariantNames;
 
-#[async_trait(?Send)]
 pub trait Resource: Clone {
     type PropName: FromStr + VariantNames + Clone;
     type Prop: Serialize + for<'de> Deserialize<'de> + fmt::Debug + InvalidProperty;