fenr 1.5.1

• Attempted to fix a bizarre error message on Bioconductor's test machines with older version of MacOS. Windows and Linux are not affected; my laptop running Sequoia 5.2 does not show show errors. I suspect a memory leak in older systems. The error vector memory limit of 64.0 Gb reached, see mem.maxVSize() happened in the function parse_kegg_genes(), a flat-file parser for KEGG. It occurred around the call tidyr::separate(), which I replaced with an alternative approach. Will see if the error is fixed.