Remove duplicate server/integration_test.go

This file was a full integration test that duplicated functionality
now comprehensively covered by tests/integration/:

- Schema operations → ddl_test.go:TestDDLSchemas
- Table operations → ddl_test.go:TestDDLCreateTable + catalog_test.go
- Data operations → dml_test.go:TestDMLInsert/Update/Delete
- Metadata queries → catalog_test.go
- Transactions → protocol_test.go:TestProtocolTransactions + session_test.go
- Commented queries → covered implicitly by protocol tests

The remaining unit tests in server/ (conn_test.go, ducklake_test.go,
etl_patterns_test.go) test internal helper functions and should stay.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <[email protected]>

Author: fuziontech