Update configure-authentication-oauth-tokens.md

Minor grammatical error in doc-strings

Author: tanmaychimurkar

articles/app-service/configure-authentication-oauth-tokens.md

@@ -79,7 +79,7 @@ If a user revokes the permissions granted to your app, your call to `/.auth/me`
 
 ## Extend session token expiration grace period
 
-The authenticated session expires after 8 hours. After an authenticated session expires, there is a 72-hour grace period by default. Within this grace period, you're allowed to refresh the session token with App Service without reauthenticating the user. You can just call `/.auth/refresh` when your session token becomes invalid, and you don't need to track token expiration yourself. Once the 72-hour grace period is lapses, the user must sign in again to get a valid session token.
+The authenticated session expires after 8 hours. After an authenticated session expires, there is a 72-hour grace period by default. Within this grace period, you're allowed to refresh the session token with App Service without reauthenticating the user. You can just call `/.auth/refresh` when your session token becomes invalid, and you don't need to track token expiration yourself. Once the 72-hour grace period lapses, the user must sign in again to get a valid session token.
 
 If 72 hours isn't enough time for you, you can extend this expiration window. Extending the expiration over a long period could have significant security implications (such as when an authentication token is leaked or stolen). So you should leave it at the default 72 hours or set the extension period to the smallest value.