fix clickhouse v2 dsn

[D3luxee]

The version 0.4.4 is not working for clickhouse anymore due to changes in the clickhouse v2 driver.

Previously the dsn was expected to start with tcp:// as seen in https://github.com/ClickHouse/clickhouse-go/tree/v1#dsn But for v2 its clickhouse:// as seen here: https://github.com/ClickHouse/clickhouse-go/tree/v2#dsn

By removing this case statement it should work again with the v2 driver.

I was not able to test this because i had to build images etc. to run it in our test setup. But according to the documentation i expect this to work.