style(rubocop): fix all safe auto correctable offenses

app/models/webhook_event.rb

@@ -15,18 +15,18 @@
 class WebhookEvent < ApplicationRecord
 
   EVENTS = [
-    'MessageSent',
-    'MessageDelayed',
-    'MessageDeliveryFailed',
-    'MessageHeld',
-    'MessageBounced',
-    'MessageLinkClicked',
-    'MessageLoaded',
-    'DomainDNSError'
+    "MessageSent",
+    "MessageDelayed",
+    "MessageDeliveryFailed",
+    "MessageHeld",
+    "MessageBounced",
+    "MessageLinkClicked",
+    "MessageLoaded",
+    "DomainDNSError"
   ]
 
   belongs_to :webhook
 
-  validates :event, :presence => true
+  validates :event, presence: true
 
 end