[9.3] Update elastic/beats and align beats-bump automation

[jeniawhite]

What

Backport the dedicated beats-bump automation to 9.3 and bump elastic/beats to the latest 9.3 commit.

Why

The update-beats workflow (on main) checks out each active branch and runs updatecli apply --config .ci/updatecli/updatecli.d/update-beats.yml. That config is read from the checked-out branch, but 9.3 still had the old config (requiredEnv "GIT_BRANCH" + scms/actions), while the new workflow sets BRANCH_NAME and runs --commit=false. So the update-beats (9.3) job failed at config load:

template: cfg:3:32: executing "cfg" at <requiredEnv "GIT_BRANCH">: error calling requiredEnv: no value found for environment variable GIT_BRANCH

How

• .ci/updatecli/updatecli.d/update-beats.yml: replace with the file-edit-only config the new workflow expects.
• .github/workflows/updatecli.yml: remove beats from the matrices (now owned by the dedicated workflow).
• go.mod/go.sum: bump to beats 9.3 tip.

No Go source changes are needed on 9.3: the otelconsumer package still exists at the old path in beats 9.3, and Manager.Start already carries //nolint:staticcheck.

Verification (local, real toolchain)

• go mod tidy, go build ./... (GOEXPERIMENT=jsonv2), and go vet on the observer-using packages → all pass.

🤖 Generated with Claude Code

[mergify]

This pull request is now in conflicts. Could you fix it? 🙏
To fixup this pull request, you can check out it locally. See documentation: https://help.github.com/articles/checking-out-pull-requests-locally/

git fetch upstream
git checkout -b evgb-bump-beats-9.3 upstream/evgb-bump-beats-9.3
git merge upstream/9.3
git push upstream evgb-bump-beats-9.3