fix typo in README

README.md

@@ -53,7 +53,7 @@ More docs for running dex as a Kubernetes authenticator can be found [here](Docu
 
 ## Connectors
 
-When a user logs in through dex, the user's identity is usually stored in another user-management system: a LDAP directory, a GitHub org, etc. Dex acts a shim between a client app and the upstream identity provider. The client only needs to understand OpenID Connect to query dex, while dex implements an array of protocols for querying other user-management systems.
+When a user logs in through dex, the user's identity is usually stored in another user-management system: a LDAP directory, a GitHub org, etc. Dex acts as a shim between a client app and the upstream identity provider. The client only needs to understand OpenID Connect to query dex, while dex implements an array of protocols for querying other user-management systems.
 
 ![](Documentation/img/dex-flow.png)