consider removing `LICENSE` from track-wide files

Currently, this repo has a `LICENSE` file in the track-wide files. That is, last year, we changed the `LICENSE` in every track repo to contain:

https://github.com/exercism/org-wide-files/blob/f208e7b54ccc67adf249a558d803af297d076715/tracks-files/LICENSE#L3

My understanding is that this is bad, because:
1. The main point of the date is to indicate when the oldest code might start to become public domain.
1. The start of the date range is more important than adding the current year - you don't have to append the current year to assert copyright ownership.
1. In general, the current year is not a "copyrightable year" for every track repo.

Therefore the date in each track repo's `LICENSE` should be specific to that repo, and `LICENSE` should not be in `org-wide-files`. Instead, I think we should update every track repo `LICENSE` to include the year of that repo's creation, and then add the `LICENSE` to `CODEOWNERS` so that it requires admin approval to change.

If desired, we could automate appending the current year to each copyright notice when a repo receives "copyrightable changes" in that year. But that's less important.

Additional complication: for older repos, maybe it should be like:
```
Copyright (c) 2014 Exercism, Inc
Copyright (c) 2019, 2021 Exercism
```

See also:
- https://github.com/exercism/problem-specifications/pull/1930
- https://github.com/exercism/nim/pull/304
- https://writing.kemitchell.com/2016/09/21/MIT-License-Line-by-Line.html
- https://opensource.stackexchange.com/questions/5778/why-do-licenses-such-as-the-mit-license-specify-a-single-year