Ignore extra kwargs on perform() in WebhooksManagerJob

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What this PR does

This changes the perform() method of WebhooksManagerJob to accept-and-ignore additional keyword arguments.

One of the things we noticed during upgrade from v18 to >=v19 is that https://github.com/Shopify/shopify_app/blob/main/lib/shopify_app/jobs/webhooks_manager_job.rb#L9 used to take a webhooks parameter to the function, but no longer does. This manifests in errors where webhooks that have been registered with Core pre-upgrade include that parameter on delivery, and so error out.

I plan on porting this fix to v19.1 branch and v20 branch along with main, since I think it's a useful change and removes a gotcha for upgrades.

Reviewer's guide to testing

• Install a version of the app that is on an older (v18) version which has webhook(s) registered. For example, a app/uninstalled handler;
• Upgrade the application to v19 or v20
• Uninstall the app (assuming app/uninstalled webhooks are registered!)
• The webhook should not generate error(s) anymore

Checklist

Before submitting the PR, please consider if any of the following are needed:

• Update CHANGELOG.md if the changes would impact users
• Update README.md, if appropriate.
• Update any relevant pages in /docs, if necessary
• For security fixes, the Disclosure Policy must be followed.