fix: the webhook url to be text (#13157)

## Description
Change the url type from string to text, to support more than 255
characters

Fixes # (issue)
https://app.chatwoot.com/app/accounts/1/conversations/65240

## Type of change

Please delete options that are not relevant.

- [ ] Bug fix (non-breaking change which fixes an issue)


## Checklist:

- [ ] My code follows the style guidelines of this project
- [ ] I have performed a self-review of my code
- [ ] I have commented on my code, particularly in hard-to-understand
areas
- [ ] I have made corresponding changes to the documentation
- [ ] My changes generate no new warnings
- [ ] I have added tests that prove my fix is effective or that my
feature works
- [ ] New and existing unit tests pass locally with my changes
- [ ] Any dependent changes have been merged and published in downstream
modules

app/models/webhook.rb

@@ -5,7 +5,7 @@
 #  id            :bigint           not null, primary key
 #  name          :string
 #  subscriptions :jsonb
-#  url           :string
+#  url           :text
 #  webhook_type  :integer          default("account_type")
 #  created_at    :datetime         not null
 #  updated_at    :datetime         not null