chore: Switch to web-push gem (#6390)

- The previous gem, `webpush` was last updated a while ago. Also, with the recent ruby upgrade, we needed a fix for zaru/webpush#106. Hence switching to the `web-push` gem where the issues are fixed.

spec/services/notification/push_notification_service_spec.rb

@@ -7,7 +7,7 @@ describe Notification::PushNotificationService do
   let(:fcm_double) { double }
 
   before do
-    allow(Webpush).to receive(:payload_send).and_return(true)
+    allow(WebPush).to receive(:payload_send).and_return(true)
     allow(FCM).to receive(:new).and_return(fcm_double)
     allow(fcm_double).to receive(:send).and_return({ body: { 'results': [] }.to_json })
   end
@@ -18,7 +18,7 @@ describe Notification::PushNotificationService do
         create(:notification_subscription, user: notification.user)
 
         described_class.new(notification: notification).perform
-        expect(Webpush).to have_received(:payload_send)
+        expect(WebPush).to have_received(:payload_send)
         expect(FCM).not_to have_received(:new)
       end
     end
@@ -29,7 +29,7 @@ describe Notification::PushNotificationService do
 
         described_class.new(notification: notification).perform
         expect(FCM).to have_received(:new)
-        expect(Webpush).not_to have_received(:payload_send)
+        expect(WebPush).not_to have_received(:payload_send)
       end
     end
   end