refs #21603 [finc] remove duplicate Key wikimedia/composer-merge-plugin in composer.json

composer.json

@@ -74,8 +74,7 @@
         "zendframework/zendrest": "2.0.2",
         "zendframework/zendservice-amazon": "2.3.1",
         "zendframework/zendservice-recaptcha": "3.2.0",
-        "zf-commons/zfc-rbac": "2.6.3",
-        "wikimedia/composer-merge-plugin": "^1.4"
+        "zf-commons/zfc-rbac": "2.6.3"
     },
     "require-dev": {
         "behat/mink": "1.7.1",