Update custom-installers.md

doc/articles/custom-installers.md

@@ -84,7 +84,7 @@ Example:
         "class": "phpDocumentor\\Composer\\TemplateInstallerPlugin"
     },
     "require": {
-        "composer-plugin-api": "1.0.0"
+        "composer-plugin-api": "^1.0"
     }
 }
 ```