message: Update reportDir flag documentation in benchmark README
diff: @@ -11,7 +11,7 @@ To run benchmarks defined using these tools, invoke mocha normally, but add the
  > `--expose-gc --perfMode --fgrep @Benchmark --reporter @fluid-tools/benchmark/dist/MochaReporter.js`
  -To configure the reporter output directory, you can add `--reporter-options reportDir=./benchmarks`
  +To configure the reporter output directory, you can add `--reportDir ./benchmarks`
  To filter to a specific `BenchmarkType` such as `Measurement` you can use it as the `--fgrep` instead:
  