When deleting contract sub, don't delete underlying webhook

[0xFirekeeper]

Unexpected behavior, we have apis for deleting webhooks

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PR-Codex overview

This PR focuses on simplifying the removeContractSubscription function by removing the deletion of a webhook associated with a contract subscription.

Detailed summary

• Removed the import statement for deleteWebhook.
• Eliminated the conditional check and call to deleteWebhook based on contractSubscription.webhookId.

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