fix(ci): force-push bump branch to handle pre-existing remote

[jbachorik]

What does this PR do?:
Changes the bump-branch push in release.sh from a plain push to --force-with-lease, so it succeeds when the remote branch already exists from a previous partial release run.

Motivation:
After the fix in #561 (skip tag/branch creation when the tag already exists), the create-release job now advances to the version-bump step correctly. However, the bump branch (e.g. automated/bump-1-44-0) may already exist on the remote from the previous run, causing a non-fast-forward rejection:

! [rejected]  automated/bump-1-44-0 -> automated/bump-1-44-0 (non-fast-forward)

--force-with-lease is safe here: the branch is always machine-generated with no human commits, and the lease ensures we don't clobber unexpected pushes from a third party.

Additional Notes:
This is a follow-up to #561, completing the recovery path for a release where the previous run left a stale bump branch.

How to test the change?:
Trigger the Validated Release workflow (release_type=minor, dry_run=false) when both the version tag and the bump branch already exist on the remote — the job should complete without error.

For Datadog employees:

• If this PR touches code that signs or publishes builds or packages, or handles
  credentials of any kind, I've requested a review from @DataDog/security-design-and-guidance.
• This PR doesn't touch any of that.
• JIRA: [JIRA-XXXX]

[dd-octo-sts]

CI Test Results

Run: #26639187778 | Commit: 540a4aa | Duration: 11m 51s (longest job)

✅ All 32 test jobs passed

Status Overview

JDK	glibc-aarch64/debug	glibc-amd64/debug	musl-aarch64/debug	musl-amd64/debug
8	-	✅	-	-
8-ibm	-	✅	-	-
8-j9	✅	✅	-	-
8-librca	-	-	✅	✅
8-orcl	-	✅	-	-
11	-	✅	-	-
11-j9	✅	✅	-	-
11-librca	-	-	✅	✅
17	✅	✅	-	-
17-graal	✅	✅	-	-
17-j9	✅	✅	-	-
17-librca	-	-	✅	✅
21	✅	✅	-	-
21-graal	✅	✅	-	-
21-librca	-	-	✅	✅
25	✅	✅	-	-
25-graal	✅	✅	-	-
25-librca	-	-	✅	✅

Legend: ✅ passed | ❌ failed | ⚪ skipped | 🚫 cancelled

Summary: Total: 32 | Passed: 32 | Failed: 0

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Updated: 2026-05-29 13:26:45 UTC