docs: fix argument typo in oauth2 code example (#763)

diff --git a/docs/oauth-installed.md b/docs/oauth-installed.md
index c5f3caf..322d678 100644
--- a/docs/oauth-installed.md
+++ b/docs/oauth-installed.md
@@ -78,7 +78,7 @@
 
 flow = InstalledAppFlow.from_client_secrets_file(
     'client_secret.json',
-    scope=['https://www.googleapis.com/auth/drive.metadata.readonly'])
+    scopes=['https://www.googleapis.com/auth/drive.metadata.readonly'])
 ```
 
 Your application uses the client object to perform OAuth 2.0 operations, such as generating authorization request URIs and applying access tokens to HTTP requests.