Extra Space Before "stackTrace" in Error Payload JSON

[math-hiyoko]

Describe the issue

I noticed that the error payload JSON generated by aws::lambda_runtime::invocation_response::failure includes an unexpected space before the "stackTrace" key. This extra space seems unnecessary and affects the consistency of the JSON format output. https://github.com/awslabs/aws-lambda-cpp/blob/934d2547fd573ece89ccbdaad2161a7e4d46fd1e/src/runtime.cpp#L530

Expected behavior

I expected the JSON output not to include unnecessary spaces before any keys to maintain consistency and compactness of the format. The preferable output should be: {"errorMessage":"message of error","errorType":"type of error","stackTrace":[]}