Replace nexB GitHub references with aboutcode-org references

### Description

> Please leave a brief description of the bug or feature request:

When scanning I see references in the JSON output that still uses the nexB GitHub org:

```
"rule_url": "https://github.com/nexB/scancode-toolkit/tree/develop/src/licensedcode/data/rules/gpl-2.0_147.RULE"
```

This should be:

```
"rule_url": "https://github.com/aboutcode-org/scancode-toolkit/tree/develop/src/licensedcode/data/rules/gpl-2.0_147.RULE"
```

Probably such a change would also require changing many tests.

### How To Reproduce

> Tell us how to reproduce the issue.

### System configuration

> For bug reports, it really helps us to know:

* What OS are you running on? (Windows/MacOS/Linux)
* What version of scancode-toolkit was used to generate the scan file?
* What installation method was used to install/run scancode? (pip/source download/other)