Remove no longer needed regexManagers (#729)

Author: strangelookingnerd

.github/renovate.json

@@ -9,14 +9,6 @@
   "reviewers": [
     "team:core"
   ],
-  "regexManagers": [
-    {
-      "fileMatch": ["common-files/.mvn/extensions.xml"],
-      "matchStrings": ["<version>(?<currentValue>.*?)<\/version>"],
-      "depNameTemplate": "io.jenkins.tools.incrementals:git-changelist-maven-extension",
-      "datasourceTemplate": "maven"
-    }
-  ],
   "labels": [
     "dependencies"
   ],