chore(deps): update opis/json-schema requirement in /tools/src/test/php

Updates the requirements on [opis/json-schema](https://github.com/opis/json-schema) to permit the latest version.
- [Release notes](https://github.com/opis/json-schema/releases)
- [Commits](opis/json-schema@2.4.1...2.6.0)

---
updated-dependencies:
- dependency-name: opis/json-schema
  dependency-version: 2.6.0
  dependency-type: direct:production
...

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

Author: dependabot[bot]

tools/src/test/php/composer.json

@@ -5,7 +5,7 @@
     "ext-dom": "*",
     "ext-json": "*",
     "ext-libxml": "*",
-    "opis/json-schema": "2.4.1"
+    "opis/json-schema": "2.6.0"
   },
   "require-dev": {
     "roave/security-advisories": "dev-latest"