Update wp-cli/wp-cli-tests requirement from ^4 to ^5

Updates the requirements on [wp-cli/wp-cli-tests](https://github.com/wp-cli/wp-cli-tests) to permit the latest version.
- [Release notes](https://github.com/wp-cli/wp-cli-tests/releases)
- [Commits](wp-cli/wp-cli-tests@v4.0.0...v5.0.0)

---
updated-dependencies:
- dependency-name: wp-cli/wp-cli-tests
  dependency-version: 5.0.0
  dependency-type: direct:development
...

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

Author: dependabot[bot]

composer.json

@@ -8,7 +8,7 @@
         "wp-cli/wp-cli": "^2"
     },
     "require-dev": {
-        "wp-cli/wp-cli-tests": "^4"
+        "wp-cli/wp-cli-tests": "^5"
     },
     "config": {
         "process-timeout": 7200,