Updated expected error message in file_credentials_test

Author: t0shiii

test/instance_agent/file_credentials_test.rb

@@ -53,7 +53,7 @@ class FileCredentialsTest < InstanceAgentTestCase
     end
 
     should 'raise error when credential file is missing' do
-      assert_raised_with_message("Failed to load credentials from path #{credentials_path}", RuntimeError) do
+      assert_raised_with_message("Profile `default' not found in #{credentials_path}", Aws::Errors::NoSuchProfileError) do
         InstanceAgent::FileCredentials.new(credentials_path)
       end
     end