TUT: update old keywords

tutorials/multiphase/interIsoFoam/sphereInReversedVortexFlow/system/setAlphaFieldDict

@@ -18,6 +18,6 @@ FoamFile
 field       "alpha.water";
 type        sphere;
 radius      0.15;
-centre      (0.35 0.35 0.35);
+origin      (0.35 0.35 0.35);
 
 // ************************************************************************* //

tutorials/multiphase/interIsoFoam/standingWave/system/setAlphaFieldDict

@@ -19,7 +19,7 @@ field       alpha.water;
 type        sin;
 direction   (1 0 0);
 up          (0 0 1);
-centre      (-0.5 0 0.5);
+origin      (-0.5 0 0.5);
 period      2;
 amplitude   0.05;
 

tutorials/multiphase/interPhaseChangeFoam/cavitatingBullet/system/snappyHexMeshDict

@@ -46,7 +46,7 @@ geometry
     refinement1
     {
         type   sphere;
-        centre (0 0 0.0025);
+        origin (0 0 0.0025);
         radius 0.0075;
     }