Migrate Jira Connect application settings to "integrations" JSON column

As per https://docs.gitlab.com/ee/development/application_settings.html we should migrate all pre-existing Jira Connect application settings to the integrations column:

• jira_connect_application_key
• jira_connect_proxy_url
• jira_connect_public_key_storage_enabled