fix: keep slahing mode default to enable (#263)

To avoid breaking the tests we should not change the default value for
the slashing mode.

Bring back `Enabled` as the default slashing mode value.

operator/pallets/external-validator-slashes/src/lib.rs

@@ -188,9 +188,9 @@ pub mod pallet {
     #[apply(derive_storage_traits)]
     #[derive(MaxEncodedLen, DecodeWithMemTracking, Default)]
     pub enum SlashingModeOption {
+        #[default]
         Enabled,
         LogOnly,
-        #[default]
         Disabled,
     }