Fix minor docs typo (facebook#2500)

Author: AlexxNica

packages/react-scripts/template/README.md

@@ -1082,7 +1082,7 @@ The watcher includes an interactive command-line interface with the ability to r
 
 ### Version Control Integration
 
-By default, when you run `npm test`, Jest will only run the tests related to files changed since the last commit. This is an optimization designed to make your tests runs fast regardless of how many tests you have. However it assumes that you don’t often commit the code that doesn’t pass the tests.
+By default, when you run `npm test`, Jest will only run the tests related to files changed since the last commit. This is an optimization designed to make your tests run fast regardless of how many tests you have. However it assumes that you don’t often commit the code that doesn’t pass the tests.
 
 Jest will always explicitly mention that it only ran tests related to the files changed since the last commit. You can also press `a` in the watch mode to force Jest to run all tests.