[pnm][gridgeometry] Use std::array instead of std::vector

dumux/discretization/porenetwork/fvelementgeometry.hh

@@ -295,7 +295,7 @@ private:
                                          std::move(unitOuterNormal),
                                          gridGeometry().throatCrossSectionalArea(gridGeometry().elementMapper().index(element)),
                                          scvfLocalIdx++,
-                                         std::vector<LocalIndexType>({0, 1}));
+                                         std::array<LocalIndexType, 2>({0, 1}));
     }
 
     //! The bound element

dumux/discretization/porenetwork/gridgeometry.hh

@@ -618,7 +618,7 @@ public:
                                                    std::move(unitOuterNormal),
                                                    this->throatCrossSectionalArea(this->elementMapper().index(element)),
                                                    scvfLocalIdx++,
-                                                   std::vector<LocalIndexType>({0, 1}));
+                                                   std::array<LocalIndexType, 2>({0, 1}));
         }
     }
 

dumux/discretization/porenetwork/subcontrolvolumeface.hh

@@ -80,12 +80,12 @@ public:
                             const GlobalPosition& unitOuterNormal,
                             const Scalar& area,
                             GridIndexType scvfIndex,
-                            std::vector<LocalIndexType>&& scvIndices)
+                            std::array<LocalIndexType, 2>&& scvIndices)
     : center_(center),
       unitOuterNormal_(unitOuterNormal),
       area_(area),
       scvfIndex_(scvfIndex),
-      scvIndices_({scvIndices[0], scvIndices[1]})
+      scvIndices_(std::move(scvIndices))
     {}
 
     //! The center of the sub control volume face