fix: check bazel versions for stable/unstable

lib/manager/bazel/package.js

 const semver = require('semver');
+const stable = require('semver-stable');
 const { getRepoTags, getRepoReleases } = require('../../datasource/github');
 
 module.exports = {
@@ -20,9 +21,19 @@ async function getPackageUpdates(config) {
       return [];
     }
     const repo = remote.substring(githubHost.length).replace(/.git$/, '');
-    const tags = await getRepoTags(repo);
+    let tags = await getRepoTags(repo);
+    logger.debug({ tags, remote });
+    // istanbul ignore if
+    if (!tags.length) {
+      logger.warn({ repo }, 'No tags found');
+      return [];
+    }
+    if (stable.is(currentVersion)) {
+      tags = tags.filter(tag => stable.is(tag));
+    }
     const [newestTag] = tags.slice(-1);
-    if (semver.gt(newestTag, currentVersion)) {
+    if (newestTag && semver.gt(newestTag, currentVersion)) {
+      logger.debug({ newestTag }, 'Found newer tag');
       return [
         {
           newVersion: newestTag,