Fix empty year generated copyright

[Bogdan Drutu]

Currently if the year is set to empty string -y="" the first header will have two consecutive empty spaces between Copyright and Holder.

Now:
// Copyright[ ][ ]OpenTelemetry Authors

After:
// Copyright[ ]OpenTelemetry Authors

[Bogdan Drutu]

Unfortunately the markdown decided that 2 consecutive spaces are not ok in the now example. but you can look at the raw text.