fix(docs): look up open issues on main builds for Renovate docs (#39801)

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.

This is a re-apply of ae46c57, as well
as making sure that the `GITHUB_TOKEN` is explicitly passed as
`extraEnv`, otherwise we see i.e.

```

ERROR: Error getting query results
       "err": {
         "cmd": "/bin/sh -c gh issue list --json \"title,number,url,labels\" --search \"type:Bug\" --limit 1000",
         "stderr": "gh: To use GitHub CLI in automation, set the GH_TOKEN environment variable.\n",
         "stdout": "",
         "options": {
           "encoding": "utf-8",
           "env": ["CI", "HOME", "PATH", "LANG"],
           "maxBuffer": 10485760,
           "timeout": 900000
         },
         "exitCode": 4,
         "name": "ExecError",
         "message": "Command failed: gh issue list ...\ngh: To use GitHub CLI in automation, set the GH_TOKEN environment variable.\n",
         "stack": "ExecError: Command failed: gh issue list ...\ngh: To use GitHub CLI in automation, set the GH_TOKEN environment variable.\n\n    at ..."
       }
```

As we can see, the `env` isn't automagically picking up the
`GITHUB_TOKEN`, so we should explicitly pass it.

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

Author: jamietanna

tools/docs/github-query-items.ts

@@ -46,7 +46,11 @@ async function getIssuesByIssueType(
   issueType: 'Bug' | 'Feature',
 ): Promise<ItemsEntity[]> {
   const command = `gh issue list --json "title,number,url,labels" --search "type:${issueType}" --limit 1000`;
-  const execRes = await exec(command);
+  const execRes = await exec(command, {
+    extraEnv: {
+      GITHUB_TOKEN: process.env.GITHUB_TOKEN,
+    },
+  });
   const res = GhOutput.safeParse(JSON.parse(execRes.stdout));
   if (res.error) {
     throw res.error;
@@ -78,7 +82,20 @@ 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 {