issues-179 Fix clippy warning

Author: ikrivosheev

src/query/on_conflict.rs

@@ -1,6 +1,6 @@
 use crate::{DynIden, Expr, IntoIden, SimpleExpr, Value};
 
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, Default)]
 pub struct OnConflict {
     pub(crate) target: Option<OnConflictTarget>,
     pub(crate) action: Option<OnConflictAction>,
@@ -226,12 +226,3 @@ impl OnConflict {
         self
     }
 }
-
-impl Default for OnConflict {
-    fn default() -> Self {
-        Self {
-            target: None,
-            action: None,
-        }
-    }
-}