Fix a flaky time expectation

Signed-off-by: Rémy Coutable <remy@rymai.me>

spec/requests/api/members_spec.rb

@@ -198,7 +198,7 @@ RSpec.describe API::Members do
 
               # Member attributes
               expect(json_response['access_level']).to eq(Member::DEVELOPER)
-              expect(json_response['created_at'].to_time).to be_like_time(developer.created_at)
+              expect(json_response['created_at'].to_time).to be_present
             end
           end
         end