docs: fix typo in oauth.md (#1058)

fix typo

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Fixes #<issue_number_goes_here> 🦕

Author: jakehadar

docs/oauth.md

@@ -45,7 +45,7 @@ flow.run_local_server()
 
 ### Flow
 
-The example below uses the `Flow` class to handle the installed appplication authorization flow.
+The example below uses the `Flow` class to handle the installed application authorization flow.
 
 #### from_client_secrets_file()