GitLab

Remove the duplicate test CARv1 file that existed both in `testdata` and
`blockstore/testdata` in favour of the one in root.

Reflect change in tests.

Duplicity checked using `md5` digest:

```sh
$ md5 testdata/sample-v1.car
MD5 (testdata/sample-v1.car) = 14fcffc271e50bc56cfce744d462a9bd

$ md5 blockstore/testdata/test.car
MD5 (blockstore/testdata/test.car) = 14fcffc271e50bc56cfce744d462a9bd
```