fix: unable to override default parameters

[CAB233]

I found that the default variables couldn't be overridden：

Run ./r2-upload-action
  with:
    r2-account-id: ***
    r2-access-key-id: ***
    r2-secret-access-key: ***
    r2-bucket: ***
    source-dir: /home/runner/work/myAUR/myAUR
    destination-dir: archlinux/test
    keep-***-fresh: true
    output-***-url: true
    multipart-size: 100
    max-retries: 5
    multipart-concurrent: true
/usr/bin/docker exec  b8410f562f004919b3c2ff11fa1ed38eb158f479ec5521b2165a0015abbaf038 sh -c "cat /etc/*release | grep ^ID"
debug: Config.keepFileFresh: false

Secondly, I found that other variables with default values seem to have the same problem, such as multipart-concurrentand output-file-url. I tried to fix them the same way but it doesn't seem to work, you may need to reconfirm it.

[ryand56]

I can't reproduce this on my end, but the keep file fresh typo, I'll change
Fixed typo in b7dbb2a