refactor: remove unused dep type merge config

lib/workers/package-file/index.js

@@ -115,10 +115,7 @@ async function renovatePackageJson(input) {
     'engines',
   ];
   const depTypeConfigs = depTypes.map(depType => {
-    const depTypeConfig = configParser.mergeChildConfig(config, {
-      ...config[depType],
-    });
-    depTypeConfig.depType = depType;
+    const depTypeConfig = { ...config, depType };
     // Always pin devDependencies
     // Pin dependencies if we're pretty sure it's not a browser library
     if (