dge_workflow: fix lcf help

Right now it says that the values is used as cut off for reporting gene which is incorrect:

https://git.mpi-cbg.de/bioinfo/ngs_tools/blob/master/dge_workflow/featcounts_deseq_mf.R#L40

In fact this value is fed into the statistical modelling leading to a more strict set of results. The help should reflect that.

See:

• https://bioconductor.org/packages/release/bioc/vignettes/DESeq2/inst/doc/DESeq2.html#tests-of-log2-fold-change-above-or-below-a-threshold https://support.bioconductor.org/p/101504/