fix(docs): Just a small typo fix in the docs (gatsbyjs#10359)

Sorry for the 1 character PR. I noticed the typo on the docs website and applied the boyscout rule 😄

docs/docs/deploying-to-s3-cloudfront.md

@@ -13,7 +13,7 @@ Using the **Hosting** feature, you can deploy your application to AWS as well as
 First, we'll want to create a new Gatsby project. If you don't already have Gatsby installed, install it:
 
 ```sh
-npm install - global gatsby-cli
+npm install --global gatsby-cli
 ```
 
 Next, we'll create a new Gatsby site: