Remove 5MB minimum file size limit

[jox]

There is no need for a 5MB minimum file size limit. AWS does not set this restriction for multipart copy.

When trying to upload files smaller than 5MB the following error will occur: "The specified upload does not exist. The upload ID may be invalid, or the upload may have been aborted or completed."

This is caused by a flaw in the code of this module. But it's easily fixed.

(Regarding 5MB minimum file size limit see also: https://stackoverflow.com/questions/24839387/uploading-a-file-less-than-5mb-through-using-multipart-upload-api-to-aws-s3-buck)

[nathaniel-holder]

This PR worked for me, but note that the AWS docs specify that input file has to be more than 5MB to use the range parameter: https://docs.aws.amazon.com/AmazonS3/latest/API/API_UploadPartCopy.html#:~:text=the%20specified%20time.-,x%2Damz%2Dcopy%2Dsource%2Drange,-The%20range%20of
Seems like the AWS docs are incorrect there.