[Remix] Rename `bin` script for sourcemap upload

If there's only one `bin` script, the name is not important. We can rename it to `_sentry-upload-remix-sourcemaps` to not have the same name as the npm package anymore.

The usage would be: `npx @sentry/remix --upload-sourcemaps`

More context here: https://github.com/getsentry/sentry-javascript/issues/20422