Update phpunit/phpunit from 7.5.18 to 7.5.19

[violinist-bot]

If you have a high test coverage index, and your tests for this pull request are passing, it should be both safe and recommended to merge this update.

Here is a list of changes between the version you use, and the version this pull request updates to:

• 4263f76a3 Prepare release
• 2076dc78f Enhancement: Use actions/checkout@v2
• 6aab04011 Lets waste three more characters on a solution for a problem that should not exist
• 33585d982 Hopefully prevent execution of this script in a webserver context.
• 7a46cf1d1 Fix: Avoid using master for GitHub actions

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