Edit README.md in Benchmarks section

Summary:
Benchmarks are not located in folder benchmark. So rename folder
and buck target from 'benchmarks' to 'benchmark'.
Closes #339

Reviewed By: gkassabli

Differential Revision: D4420355

Pulled By: emilsjolander

fbshipit-source-id: 7a1bc6ece7f4b64c7cac506357e265c1b4790a4f

README.md

@@ -27,4 +27,4 @@ You may need to install the latest watir-webdriver gem (`gem install watir-webdr
 For the main C implementation of Yoga clang-format is used to ensure a consistent code style. Please run `bash format.sh` before submitting a pull request. For other languages just try to follow the current code style.
 
 ## Benchmarks
-Benchmarks are located in `benchmarks/YGBenchmark.c` and can be run with `buck run //benchmarks:benchmarks`. If you think your change has affected performance please run this before and after your change to validate that nothing has regressed. Benchmarks are run on every commit in CI.
+Benchmarks are located in `benchmark/YGBenchmark.c` and can be run with `buck run //benchmark:benchmark`. If you think your change has affected performance please run this before and after your change to validate that nothing has regressed. Benchmarks are run on every commit in CI.