Describe the bug

Follow-up of #632, which didn't fully address this issue

Adding patches to composer.json for dev dependencies seems incorrect to me, for two reasons:

a) The local patch files won't be found in the module, AFAIK composer-patches won't look there
b) Even if they would be found, the project is likely to use a different version of phpunit where the patches don't apply.

To Reproduce
Steps to reproduce the behavior:

1. composer init
2. composer require cweagans/composer-patches predis/predis
3. composer config extra.enable-patching true
4. composer require --dev phpunit/phpunit

  - Applying patches for phpunit/phpunit
    ./tests/phpunit_php7.patch (Fix PHP 7 compatibility)
   Could not apply patch! Skipping. The error was: The "./tests/phpunit_php7.patch" file could not be downloaded: failed to open stream: No such file or directory
    ./tests/phpunit_php8.patch (Fix PHP 8 compatibility)
   Could not apply patch! Skipping. The error was: The "./tests/phpunit_php8.patch" file could not be downloaded: failed to open stream: No such file or directory

Expected behavior
A clear and concise description of what you expected to happen.

Versions (please complete the following information):

• Predis: 1.1.x
• PHP 7.4
• Redis Server irrelevant
• OS: Ubuntu 20.10

I don't think it is possible to do this, not without cweagans/composer-patches introducing a patches-dev. My suggestion would be to switch to applying those patches with a script/travis commands (or whatever CI you use)