Fixed comment in patch (see #414)

patches/lammps-6Apr13.config

@@ -30,8 +30,6 @@ file *after* the relevant input parameters have been set (e.g. after "timestep"
 \bug The provided patch does not pass the virial correctly to PLUMED (see https://github.com/plumed/plumed2/issues/377).
      If you need to perform constant pressure simulations you should download a LAMMPS version newer than November 2018, where the mentioned bug
      has been fixed, that natively supports PLUMED 2.4.
-     If you need to use LAMMPS with fixed virial with PLUMED 2.3, you can compile LAMMPS with PLUMED 2.4 using runtime binding and then set the variable
-     PLUMED_KERNEL to load PLUMED 2.3.
 
 See also http://lammps.sandia.gov/doc/Section_commands.html for
 further info on processing LAMMPS input, as well as