Math/Geometry: reduce benchmark iterations.

It still runs with acceptable error but at a quarter time. The iteration
count can be always increased from command-line.

src/Magnum/Math/Geometry/Test/IntersectionBenchmark.cpp

@@ -131,7 +131,7 @@ IntersectionBenchmark::IntersectionBenchmark() {
 
                    &IntersectionBenchmark::sphereConeNaive,
                    &IntersectionBenchmark::sphereCone,
-                   &IntersectionBenchmark::sphereConeView}, 25);
+                   &IntersectionBenchmark::sphereConeView}, 10);
 
     /* Generate random data for the benchmarks */
     std::random_device rnd;