fix cli auth

[tongueroo]

Fix CLI auth.

• Remove the File.exist accessTokens.json check
• Update command to az account get-access-token -o json without the --resource option

Testing Notes

Tested the CLI auth flow:

$ exe/armrest auth cli
{
  "access_token": "bleh",
  "expires_on": 1703173056,
  "subscription": "EXAMPLE-1234-5678-9012-EXAMPLE",
  "tenant": "EXAMPLE",
  "token_type": "Bearer"
}

Also tested the app auth flow:

$ exe/armrest auth app
{
  "token_type": "Bearer",
  "expires_in": "3599",
  "ext_expires_in": "3599",
  "expires_on": "1703172804",
  "not_before": "1703168904",
  "resource": "https://management.azure.com",
  "access_token": "blah"
}

Closes #3 #4

[tongueroo]

Released in 0.2.0