Fix result type

[lowtower]

Provide a narrative description of what you are trying to accomplish:

• Are you fixing a bug?
  • Detail how the bug is invoked currently.

phpstan raises an error saying that ResulSetInterface has no method current().

• Detail the original, incorrect behavior.

The selectWith() method has defined the @returnType as ResultSetInterface.
The method calls the method executeSelect(), which returns ResultSet.
The return types should be the same.
removes also the @throws flag as it doesn't throw an exception itself, but just the called methods.

• Detail the new, expected behavior.

• Base your feature on the master branch, and submit against that branch.

• Add a regression test that demonstrates the bug, and proves the fix.

• Add a CHANGELOG.md entry for the fix.

• Are you creating a new feature?

  • Why is the new feature needed? What purpose does it serve?
  • How will users use the new feature?
  • Base your feature on the develop branch, and submit against that branch.
  • Add only one feature per pull request; split multiple features over multiple pull requests
  • Add tests for the new feature.
  • Add documentation for the new feature.
  • Add a CHANGELOG.md entry for the new feature.

• Is this related to quality assurance?

• Is this related to documentation?

New PR as requested by @ezimuel when closing #312.

[ezimuel]

@lowtower thanks!