Fixing delete

Delete invoker implicit signature:
```scala
implicit def queryToDeleteInvoker(q: Query[_ <: Table[_], _]): DeleteInvoker = ...
```

Requires first argument to be of type `Table[_]`.

Implicit for `run` method does not have this requirement:
```scala
implicit def queryToQueryExecutor[U](q: Query[_, U]): QueryExecutor[Seq[U]] = ...
```