ci(build-and-test-differential): fix fetch depth

[xmfcx]

Description

Similar to:

https://github.com/autowarefoundation/autoware.universe/blob/82a10de1f7b49eeeb80108ea3aa6a477d79220f5/.github/workflows/build-and-test-differential.yaml#L39-L46

It will fetch the PR commits for the modified files workflow to function.

For mor details, see:

• https://github.com/autowarefoundation/autoware-github-actions/blob/92b81882b5e5a67da07211aa997f61f7d9f94be7/get-modified-packages/README.md#fetch-only-the-pr-branch-and-all-pr-commits

Related links

Fixes:

• https://github.com/autowarefoundation/autoware_tools/actions/runs/9552231579/job/26328319273?pr=54#step:6:21

Tests performed

It passes.

This is not a good test since this is only a single commit and there are no modified packages.

But this is used like this in Universe repository and tested extensively there.

Notes for reviewers

Interface changes

Effects on system behavior

Pre-review checklist for the PR author

The PR author must check the checkboxes below when creating the PR.

• I've confirmed the contribution guidelines.
• The PR follows the pull request guidelines.

In-review checklist for the PR reviewers

The PR reviewers must check the checkboxes below before approval.

• The PR follows the pull request guidelines.
• The PR has been properly tested.
• The PR has been reviewed by the code owners.

Post-review checklist for the PR author

The PR author must check the checkboxes below before merging.

• There are no open discussions or they are tracked via tickets.
• The PR is ready for merge.

After all checkboxes are checked, anyone who has write access can merge the PR.

[xmfcx]

I've added all the necessary information to explain how this will fix the issue. Since I've worked on this CI issue a lot and also I caused the issue, I will merge right away and rebase some other PRs to make sure people are not blocked.