License "GPL-2.0+" is a deprecated SPDX license identifier

Problem/Motivation

This project includes a composer.json file that declares "license": "GPL-2.0+" (code hosted on Drupal.org must be licensed GPL 2.0 or later).

Composer has a CLI command called "validate" to check if a composer.json file is valid. When running it on my project, I see...

$ composer validate -A
  ... a bunch of output for my root composer.json and other modules I have installed ...
drupal/views_data_export is valid, but with a few warnings
# General warnings
- License "GPL-2.0+" is a deprecated SPDX license identifier, use "GPL-2.0-or-later" instead
  ... a bunch more output for other modules I have installed ...

I see the SPDX list of licenses shows GPL-2.0+ in the deprecated list.

Steps to reproduce

1. Make sure you are running at least composer version 2.1 (tested on composer 2.7.0 on 2024-02-08): composer --version
2. Create a Drupal project: composer create-project drupal/recommended-project:10.2.3 "3209680-testing"
3. Change to the Drupal project directory: cd 3209680-testing
4. Install the latest version of views_data_export: composer require --prefer-install=source 'drupal/views_data_export:dev-8.x-1.x@dev'
5. Run composer validate -A (look for drupal/views_data_export in the output
   • Expected behavior: drupal/views_data_export is valid
   • Actual behavior:
     

     drupal/views_data_export is valid, but with a few warnings
     # General warnings
     - License "GPL-2.0+" is a deprecated SPDX license identifier, use "GPL-2.0-or-later" instead

Proposed resolution

Modify /composer.json, changing "license": "GPL-2.0+", to "license": "GPL-2.0-or-later",.

Remaining tasks

1. Write a patch (done by @voleger in #2)
2. Review and feedback (done by @mparker17 in #4)
3. RTBC and feedback
4. Commit

User interface changes

None.

API changes

None.

Data model changes

None.