fix dependabot version update workflow

[rtpascual]

Problem

There were some issues and the handle_dependabot_version_update workflow was not able to add a changeset file to Dependabot PRs.

Issue number, if available:

Changes

• Update getting the branch name and sha from GitHub context (this removed the need for HEAD_SHA input for the script)
• Added fetch depth to checkout step so we can properly get the updated files

Corresponding docs PR, if applicable:

Validation

This PR #2393 that has these changes and is based off of this Dependabot version update PR #2387.
https://github.com/aws-amplify/amplify-backend/actions/runs/12588139778/job/35085511871

Checklist

• If this PR includes a functional change to the runtime behavior of the code, I have added or updated automated test coverage for this change.
• If this PR requires a change to the Project Architecture README, I have included that update in this PR.
• If this PR requires a docs update, I have linked to that docs PR above.
• If this PR modifies E2E tests, makes changes to resource provisioning, or makes SDK calls, I have run the PR checks with the run-e2e label set.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[changeset-bot]

⚠️ No Changeset found

Latest commit: a2ab4cf

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

This PR includes no changesets

When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types

Click here to learn what changesets are, and how to add one.

Click here if you're a maintainer who wants to add a changeset to this PR