CI: Update path to repositories when using actions/checkout action

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This targets all the repos in the maliput ecosystem

### Summary

We are using
```sh
- uses: actions/checkout@v2
with:
repository: ToyotaResearchInstitute/maliput
fetch-depth: 0
path: ${{ env.ROS_WS }}/src/maliput
token: ${{ secrets.MALIPUT_TOKEN }}
```
for each dependency.

Let's use `maliput/maliput` instead of `ToyotaResearchInstitute/maliput`

### Alternative
We could directly handle it via `dependencies.repos` file and remove all the `actions/checkout` actions making the workflow a bit simpler.

Start by locating the workflow files containing the actions/checkout snippets for the maliput dependencies, then inspect the dependencies.repos file mentioned as an alternative. Update the repository paths consistently across the targeted repositories and verify that the workflows still check out dependencies into the expected workspace locations.

Written by the indexing model from the issue text.