message: fix google benchmark README so it works in CLion
diff: @@ -712,6 +712,7 @@ or where there are only a couple of lines per benchmark. Here's an example of
  the default output:
  ```
  +
  ------------------------------------------------------------------------------
  Benchmark Time CPU Iterations UserCounters...
  ------------------------------------------------------------------------------
  @@ -740,6 +741,7 @@ individual benchmarks. Here's an example of corresponding output when
  `--benchmark_counters_tabular=true` is passed:
  ```
  +
  ---------------------------------------------------------------------------------------
  Benchmark Time CPU Iterations Bar Bat Baz Foo
  ---------------------------------------------------------------------------------------
  