release: sourcegraph@3.40.2

Created by: caugustus-sourcegraph

This pull request is part of the Sourcegraph 3.40.2 release.

• Release batch change
• Tracking issue

Additional changes required

These steps must be completed before this PR can be merged, unless otherwise stated. Push any required changes directly to this PR branch.

• Update the CHANGELOG to include all the changes included in this patch. Learn more about how to update CHANGELOG.md.
• If any specific upgrade steps are required, update the upgrade guides in doc/admin/updates
• Ensure all other pull requests in the batch change have been merged
• Run yarn run release release:finalize to generate the tags required. CI will not pass until this command is run.
• Re-run the build on this branch (using either sg ci build --wait or the Buildkite UI) and merge when the build passes.

cc @sashaostrikov

Test plan

CI checks in this repository should pass, and a manual review should confirm if the generated changes are correct