fix: filter tags in getRepoTags request

lib/datasource/github.js

@@ -12,8 +12,9 @@ function semverSort(a, b) {
 
 async function getRepoTags(repo) {
   try {
-    const url = `repos/${repo}/git/refs?per_page=100`;
+    const url = `repos/${repo}/git/refs/tags?per_page=100`;
     const res = (await ghGot(url, { paginate: true })).body;
+    logger.trace({ res });
     const tagPrefix = 'refs/tags/';
     return res
       .filter(o => o.ref.startsWith(tagPrefix))