No copyrights recognised in "AUTHORS.txt"

### Description

I recently scanned the "jquery-3.6.0" package (https://github.com/jquery/jquery/archive/refs/tags/3.6.0.zip).
Unfortunately not a single copyright entry (name + e-mail address) from the very obvious file "AUTHORS.txt" was recognised.

### How To Reproduce

- Download the jquery package from the link above and unzip it.
- scancode -clip jquery-3.6.0/ --json-pp jquery-3.6.0.json

### System configuration

* What OS are you running on? Xubuntu Linux 20.04.2 LTS
* What version of scancode-toolkit was used to generate the scan file? 21.3.31
* What installation method was used to install/run scancode? (pip/source download/other) pip3 install scancode-toolkit[full], runing in a venv as suggested in the installation instructions