fix typo in deprecated mesh.getPhysicsRestitution method

src/Mesh/babylon.abstractMesh.js

@@ -755,7 +755,7 @@ var BABYLON;
          * @Deprecated. Use getPhysicsImpostor().getParam("restitution");
          */
         AbstractMesh.prototype.getPhysicsRestitution = function () {
-            return this.physicsImpostor.getParam("resitution");
+            return this.physicsImpostor.getParam("restitution");
         };
         AbstractMesh.prototype.getPositionInCameraSpace = function (camera) {
             if (!camera) {

src/Mesh/babylon.abstractMesh.ts

@@ -846,7 +846,7 @@
          * @Deprecated. Use getPhysicsImpostor().getParam("restitution");
          */
         public getPhysicsRestitution(): number {
-            return this.physicsImpostor.getParam("resitution")
+            return this.physicsImpostor.getParam("restitution")
         }
 
         public getPositionInCameraSpace(camera?: Camera): Vector3 {