Bump phpunit/phpunit from 8.5.14 to 9.5.3 (#13)

Bumps [phpunit/phpunit](https://github.com/sebastianbergmann/phpunit) from 8.5.14 to 9.5.3.
- [Release notes](https://github.com/sebastianbergmann/phpunit/releases)
- [Changelog](https://github.com/sebastianbergmann/phpunit/blob/master/ChangeLog-8.5.md)
- [Commits](sebastianbergmann/phpunit@8.5.14...9.5.3)

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

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

composer.json

@@ -24,7 +24,7 @@
         "app-insights-php/client": "^0.2.3"
     },
     "require-dev": {
-        "phpunit/phpunit": "^8.5",
+        "phpunit/phpunit": "^8.5 || ^9.0",
         "friendsofphp/php-cs-fixer": "^2.16"
     },
     "scripts": {