STYLE: use PstreamBuffers default construct

- PstreamBuffers are nonBlocking by default, so no need to re-specify

src/functionObjects/randomProcesses/energySpectrum/energySpectrum.C

@@ -215,7 +215,7 @@ bool Foam::functionObjects::energySpectrum::write()
 
     if (Pstream::parRun())
     {
-        PstreamBuffers pBufs(Pstream::commsTypes::nonBlocking);
+        PstreamBuffers pBufs;
 
         {
             UOPstream toMaster(Pstream::masterNo(), pBufs);