remove azureTokens.json from the credential list (#883)

Author: Michaelvll

sky/clouds/azure.py

@@ -10,7 +10,6 @@
 
 # Minimum set of files under ~/.azure that grant Azure access.
 _CREDENTIAL_FILES = [
-    'accessTokens.json',
     'azureProfile.json',
     'clouds.config',
     'config',