the 4th order solver should only need 4 ghost cells, not 5 (#248)

this also updates the benchmarks

Author: zingale

pyro/compressible_fv4/simulation.py

@@ -9,9 +9,6 @@ def __init__(self, solver_name, problem_name, rp, *,
                  timers=None, data_class=fv.FV2d):
         super().__init__(solver_name, problem_name, rp, timers=timers, data_class=data_class)
 
-    def initialize(self, *, extra_vars=None, ng=5):
-        super().initialize(extra_vars=extra_vars, ng=ng)
-
     def substep(self, myd):
         """
         compute the advective source term for the given state