Update utils-selectors.R

Hi!

The assumption that for ST arrays the fsetid and man_fsetid are the same doesn't hold true for e.g. DroGene-1_0-st

taken from "DroGene-1_0-st.mps":
probeset_id     transcript_cluster_id     probeset_list     probe_count
18130001     18130001     18130001     5
...
18130640     18130640     18130641 18130642 18130643 18130644 18130645 18130646 18130647 18130648 18130649     29
18130650     18130650     18130651 18130652 18130653 18130654 18130655 18130656 18130657 18130658     32

Using the probeTable.fsetid instead should give the expected result.

Regards &
Signed-off-by: Grischa Toedt