fix(jobs): [nan-1010] use void (#2195)

## Describe your changes
As explained by Thomas:

![image](https://github.com/NangoHQ/nango/assets/1724137/49464765-394f-4bdc-8c15-388f72704980)

Use void since we're not explicitly handling the promise resolution of
the webhook sending

Tested this against returning a 504 (what the customer is returning from
their webhook) from a webhook with Temporal and the task execution
completes even as the webhook continues to retry. With `async` usage,
the temporal activity is still in running state while the webhook
retries.

## Issue ticket number and link

## Checklist before requesting a review (skip if just adding/editing
APIs & templates)
- [ ] I added tests, otherwise the reason is: 
- [ ] I added observability, otherwise the reason is:
- [ ] I added analytics, otherwise the reason is:

packages/shared/lib/services/notification/webhook.service.ts

@@ -18,7 +18,7 @@ import { stringifyError } from '@nangohq/utils';
 
 dayjs.extend(utc);
 
-const RETRY_ATTEMPTS = 10;
+const RETRY_ATTEMPTS = 7;
 
 const NON_FORWARDABLE_HEADERS = [
     'host',

packages/shared/lib/services/sync/run.service.ts

@@ -648,7 +648,7 @@ export default class SyncRun {
             deleted
         };
 
-        await webhookService.sendSyncUpdate(
+        void webhookService.sendSyncUpdate(
             this.nangoConnection,
             this.syncName,
             model,