small fix.

Author: xhawk18

example/simple_benchmark_test.cpp

@@ -94,7 +94,6 @@ int main() {
         test_switch(io, 1).then([&]() {
             return test_switch(io, 1000);
         }).then([&]() {
-            io.stop();
             return test_switch(io, 10000);
         }).then([&]() {
             return test_switch(io, 100000);