Build(deps-dev): Bump phpunit/phpunit from 7.5.15 to 7.5.16

Bumps [phpunit/phpunit](https://github.com/sebastianbergmann/phpunit) from 7.5.15 to 7.5.16.
- [Release notes](https://github.com/sebastianbergmann/phpunit/releases)
- [Changelog](https://github.com/sebastianbergmann/phpunit/blob/7.5.16/ChangeLog-7.5.md)
- [Commits](sebastianbergmann/phpunit@7.5.15...7.5.16)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

composer.json

@@ -32,7 +32,7 @@
     "phpstan/phpstan": "~0.11.15",
     "phpstan/phpstan-deprecation-rules": "~0.11.2",
     "phpstan/phpstan-strict-rules": "~0.11.1",
-    "phpunit/phpunit": "^7.5.15",
+    "phpunit/phpunit": "^7.5.16",
     "symfony/filesystem": "^4.3.4"
   },
   "config": {