You can't perform this with just the aws command, but you can easily pipe it to another command to strip out the portion you don't want.
You also need to remove the human-readable flag to get output easier to work with, and the summarize flag to remove the summary data at the end.
follow the syntax given below:
aws s3 ls s3://<your_bucket_name> --recursive | awk '{print $4}'
And to add spaces in filenames into account, refer to the following syntax:
aws s3 ls s3://mybucket --recursive | awk '{$1=$2=$3=""; print $0}' | sed 's/^[ \t]*//'
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