Fix port conflict in .wp-env.tests.json by setting explicit testsPort

Co-authored-by: ernilambar <2098823+ernilambar@users.noreply.github.com>
Agent-Logs-Url: https://github.com/WordPress/plugin-check/sessions/7767fe7c-e3cd-4ef7-a2d0-c37fbeab9262

Author: Copilot

.wp-env.tests.json

@@ -3,5 +3,6 @@
   "core": null,
   "plugins": [ "." ],
   "phpVersion": "7.4",
-  "port": 8889
+  "port": 8889,
+  "testsPort": 8890
 }