package/openmpi: drop unrecognized option

--disable-vt has been dropped since version 2.0.0 and
https://github.com/open-mpi/ompi/commit/94190bf04b0877e878223a04c236443774e57ef2



Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>