logs: info not warn for github retrieval problem

lib/datasource/github.js

@@ -23,7 +23,7 @@ async function getDependency(repo, options = {}) {
       );
     }
   } catch (err) {
-    logger.warn(
+    logger.info(
       { repo, err, message: err.message },
       'Error retrieving from github'
     );