logs: don’t warn for lock file maintenance lerna

lib/manager/npm/post-update/index.js

@@ -604,10 +604,17 @@ async function getAdditionalFiles(config, packageFiles) {
               logger.trace('File is unchanged');
             }
           } catch (err) {
-            logger.warn(
-              { lockFilePath },
-              'No lock file found after lerna bootstrap'
-            );
+            if (config.updateType === 'lockFileMaintenance') {
+              logger.info(
+                { lockFilePath },
+                'No lock file found after lerna bootstrap'
+              );
+            } else {
+              logger.warn(
+                { lockFilePath },
+                'No lock file found after lerna bootstrap'
+              );
+            }
           }
         } else {
           logger.trace('No lock file found');