Update wp-cli/wp-cli-tests requirement from ^3.2 to ^4.0

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@v3.2.0...v4.0.1)

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

Signed-off-by: dependabot[bot] <[email protected]>

composer.json

@@ -22,7 +22,7 @@
         "wp-cli/wp-cli": "^2.1"
     },
     "require-dev": {
-        "wp-cli/wp-cli-tests": "^3.2"
+        "wp-cli/wp-cli-tests": "^4.0"
     },
     "config": {
         "platform": {