Merge pull request graphql#822 from kvoncode/patch-1

Fix: grammar typo in <Tutorial-ExpressGraphQL.md>

Author: orta

site/graphql-js/Tutorial-ExpressGraphQL.md

@@ -7,7 +7,7 @@ permalink: /graphql-js/running-an-express-graphql-server/
 next: /graphql-js/graphql-clients/
 ---
 
-The simplest way to run an GraphQL API server is to use [Express](https://expressjs.com), a popular web application framework for Node.js. You will need to install two additional dependencies:
+The simplest way to run a GraphQL API server is to use [Express](https://expressjs.com), a popular web application framework for Node.js. You will need to install two additional dependencies:
 
 ```bash
 npm install express express-graphql graphql --save