fix(docs): look up open issues on main builds for Renovate docs

We're currently always skipping the detection of open bugs/features, so
even though [0] introduced authentication to GitHub, this didn't
actually lead to the lookup when running in CI.

If we're not running in Renovate's CI build (i.e. as part of the release
process) or the docs site's CI build (as part of post-release
operations) we should continue to skip the build, when running in CI.

This also makes it clearer with a WARN log line to explain why this is
being skipped.

[0]: renovatebot/renovatebot.github.io#746

tools/docs/github-query-items.ts

@@ -78,7 +78,20 @@ export async function getOpenGitHubItems(): Promise<RenovateOpenItems> {
   }
 
   if (process.env.CI) {
-    return result;
+    if (
+      process.env.GITHUB_REF === 'main' &&
+      process.env.GITHUB_REPOSITORY !== 'renovatebot/renovatebot.github.io' &&
+      process.env.GITHUB_REPOSITORY !== 'renovatebot/renovate'
+    ) {
+      logger.warn(
+        {
+          repository: process.env.GITHUB_REPOSITORY,
+          ref: process.env.GITHUB_REF,
+        },
+        "Skipping collection of open GitHub Issues, as we're running CI on a non-HEAD branch of Renovate or its docs site",
+      );
+      return result;
+    }
   }
 
   try {