Remove obsolete intermediate variable

src/bisection-simpler-example2-gradient.cc

@@ -40,8 +40,7 @@ class SampleFunctional : public SmallFunctional<dimension> {
   // extending the interface here
   double directionalDerivative(const SmallVector x,
                                const SmallVector dir) const {
-    SmallVector grad = d(x);
-    return grad * dir;
+    return d(x) * dir;
   }
 
   SmallVector minimise(const SmallVector x, int iterations) const {