ci: grant pull-requests:read so lint-pr-title workflow starts (#255)

## Summary

Adds `permissions: pull-requests: read` at the workflow level in
`.github/workflows/lint-pr-title.yml`. The reusable workflow at
`launchdarkly/gh-actions/.github/workflows/lint-pr-title.yml@main` now
declares `pull-requests: read` at the job level (via
launchdarkly/gh-actions#86). A reusable workflow can only request a
subset of the caller's granted permissions, so without an explicit
`permissions` block here, the called job fails to start
(`startup_failure`).

Same fix as launchdarkly/sdk-meta#429, applied across SDK repositories.

## Review & Testing Checklist for Human

- [ ] Verify the `Lint PR title` check on this PR exits `success` rather
than `startup_failure`

### Notes

- `launchdarkly/php-server-sdk-otel` could not be updated due to a push
permission issue (403) and will need to be fixed separately.

Link to Devin session:
https://app.devin.ai/sessions/c7b96da5c9074500aa684bc9a9ba1c31
Requested by: @kinyoklion

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> **Low Risk**
> Low risk workflow permission tweak; it only expands the action’s read
access to PR metadata and doesn’t affect application code or
deployments.
> 
> **Overview**
> Ensures the `Lint PR title` reusable workflow can run by explicitly
granting **workflow-level** `permissions: pull-requests: read` in
`.github/workflows/lint-pr-title.yml`, avoiding `startup_failure` when
the called workflow requests PR read access.
> 
> <sup>Reviewed by [Cursor Bugbot](https://cursor.com/bugbot) for commit
484a4bf. Bugbot is set up for automated
code reviews on this repo. Configure
[here](https://www.cursor.com/dashboard/bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

Co-authored-by: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>

Author: kinyoklion

.github/workflows/lint-pr-title.yml

@@ -7,6 +7,9 @@ on:
       - edited
       - synchronize
 
+permissions:
+  pull-requests: read
+
 jobs:
   lint-pr-title:
     uses: launchdarkly/gh-actions/.github/workflows/lint-pr-title.yml@main