Transfer feature flags from group::import and integrate to group::import

As part of a reorg (internal), the groupimport and integrate no longer exists.

This MR transfers 13 feature flags from the "group::import and integrate" group to the "group::import" group.

Feature flags transferred:

• auto_disabling_web_hooks
• override_bulk_import_disabled
• bulk_import_deferred_workers
• export_reduce_relation_batch_size
• web_hook_test_api_endpoint_rate_limit
• web_hook_event_resend_api_endpoint_rate_limit
• github_user_mapping
• bitbucket_server_user_mapping
• reassignment_throttling
• new_project_creation_form
• reassignment_throttling_table_check
• group_import_history_visibility
• import_rescue_query_canceled

Relates to: Feature flags requiring attention for group::im... (gitlab-org/quality/triage-reports#27471 - closed)