[TASK] Update phpstan/phpstan-phpunit requirement from ^1.3.16 to ^1.4.0

[dependabot[bot]]

Updates the requirements on phpstan/phpstan-phpunit to permit the latest version.

Release notes

Sourced from phpstan/phpstan-phpunit's releases.

1.4.0

• f3ea021 - Update lock-closed-issues.yml
• f93aec7 - Merge remote-tracking branch 'origin/1.3.x' into 1.4.x
• 77bdf96 - Update metcalfc/changelog-generator action to v4.3.1
• 6a1df9a - Update cbrgm/mastodon-github-action action to v2
• e95a58b - Update metcalfc/changelog-generator action to v4.2.0
• 77345df - Update dessant/lock-threads action to v5
• 99bb21e - Merge branch '1.3.x' into 1.4.x
• ac8ea99 - Update actions/checkout action to v4
• 529f300 - Merge branch '1.3.x' into 1.4.x
• 62e883e - Open 1.4.x-dev
• 97ec1d3 - Merge branch '1.3.x' into 1.4.x
• 4d99a7d - Require PHPStan 1.11
• 908e232 - Error identifiers

Commits

• f3ea021 Update lock-closed-issues.yml
• f93aec7 Merge remote-tracking branch 'origin/1.3.x' into 1.4.x
• 77bdf96 Update metcalfc/changelog-generator action to v4.3.1
• 6a1df9a Update cbrgm/mastodon-github-action action to v2
• e95a58b Update metcalfc/changelog-generator action to v4.2.0
• 77345df Update dessant/lock-threads action to v5
• 99bb21e Merge branch '1.3.x' into 1.4.x
• ac8ea99 Update actions/checkout action to v4
• 529f300 Merge branch '1.3.x' into 1.4.x
• 62e883e Open 1.4.x-dev
• Additional commits viewable in compare view

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