buoyantPimpleFoam::pEqn: Moved p_rgh relaxation so that the relaxed p_rgh is used when updating p

This improves convergence of some steady-state chtMultiRegionFoam (which uses
the pEqn.H from buoyantPimpleFoam) cases but does not affect transient
simulations unless aggressive pressure relaxation is applied, i.e. transient
SIMPLE.

applications/solvers/heatTransfer/buoyantPimpleFoam/pEqn.H

@@ -98,6 +98,9 @@ else
 
 phi = phiHbyA + p_rghEqn.flux();
 
+// Explicitly relax pressure for momentum corrector
+p_rgh.relax();
+
 p = p_rgh + rho*gh + pRef;
 
 if (mesh.steady())
@@ -120,9 +123,6 @@ else
     #include "compressibleContinuityErrs.H"
 }
 
-// Explicitly relax pressure for momentum corrector
-p_rgh.relax();
-
 // Correct the momentum source with the pressure gradient flux
 // calculated from the relaxed pressure
 U = HbyA + rAU*fvc::reconstruct((phig + p_rghEqn.flux())/rhorAUf);