[bug] The secret files generated by `mapt` don't end with a EOL

The files created by `mapt` from the pulumi secrets don't end by a new line:
```
adminusername  adminuserpassword  host username  userpassword
```

As a best practice, the `\n` should be appended at the end of the file.

see the answers of https://unix.stackexchange.com/questions/18743/whats-the-point-in-adding-a-new-line-to-the-end-of-a-file
