Various code cleanup.

app/Models/Recurrence.php

@@ -28,6 +28,7 @@ use FireflyIII\User;
 use Illuminate\Database\Eloquent\Model;
 use Illuminate\Database\Eloquent\Relations\BelongsTo;
 use Illuminate\Database\Eloquent\Relations\HasMany;
+use Illuminate\Database\Eloquent\Relations\MorphMany;
 use Illuminate\Database\Eloquent\SoftDeletes;
 use Symfony\Component\HttpKernel\Exception\NotFoundHttpException;
 
@@ -112,7 +113,7 @@ class Recurrence extends Model
      * @codeCoverageIgnore
      * Get all of the notes.
      */
-    public function notes()
+    public function notes(): MorphMany
     {
         return $this->morphMany(Note::class, 'noteable');
     }