TrkVertexBilloirTools: Fix cppcheck warnings.

Useless pointer comparisons.

Tracking/TrkVertexFitter/TrkVertexBilloirTools/src/FastVertexFitter.cxx

 /*
-  Copyright (C) 2002-2020 CERN for the benefit of the ATLAS collaboration
+  Copyright (C) 2002-2021 CERN for the benefit of the ATLAS collaboration
 */
 
 /***************************************************************************
@@ -377,7 +377,6 @@ namespace Trk
  		   xAOD::Vertex* fittedVertex = fit( measuredPerigees, constraint ); 
  		 
  		   //assigning the input tracks to the fitted vertex through VxTrackAtVertices
- 		   if(fittedVertex !=nullptr) 
  		   { 
  		    if( fittedVertex->vxTrackAtVertexAvailable() ) // TODO: I don't think vxTrackAtVertexAvailable() does the same thing as a null pointer check!
  		    { 

Tracking/TrkVertexFitter/TrkVertexBilloirTools/src/FullVertexFitter.cxx

@@ -529,7 +529,6 @@ namespace Trk
  		   xAOD::Vertex* fittedVertex = fit( measuredPerigees, constraint ); 
  		 
  		   //assigning the input tracks to the fitted vertex through VxTrackAtVertices
- 		   if(fittedVertex !=nullptr) 
  		   { 
  		    if( fittedVertex->vxTrackAtVertexAvailable() ) // TODO: I don't think vxTrackAtVertexAvailable() does the same thing as a null pointer check! 
  		    {