Remove ln_login from users

Not needed anymore, removing in favor of unencrypted `ln_account`.

spec/jobs/create_lndhub_account_job_spec.rb

@@ -19,7 +19,7 @@ RSpec.describe CreateLndhubAccountJob, type: :job do
       .with { |req| req.body == '{}' }
 
     user.reload
-    expect(user.ln_login).to eq("abc123")
+    expect(user.ln_account).to eq("abc123")
     expect(user.ln_password).to eq("def456")
   end