fix(changelog): remove trailing slash in changelog url

This seems to fix #2219. It wasn’t RST.

lib/workers/pr/changelog/source-github.js

@@ -62,9 +62,9 @@ async function getChangeLogJSON({
     logger.debug('Repository URL does not match any hnown hosts');
     return null;
   }
-  const repository = pathname.slice(1);
+  const repository = pathname.slice(1).replace(/\/$/, '');
   if (repository.split('/').length !== 2) {
-    logger.info('Invalid github URL found');
+    logger.info({ repositoryUrl }, 'Invalid github URL found');
     return null;
   }
   if (!(releases && releases.length)) {