Rename initial_state in execute_circuits

[Edoardo-Pedicillo]

This PR closes #893 Checklist:

• [ ] Reviewers confirm new code works as expected.
• [ ] Tests are passing.
• [ ] Coverage does not decrease.
• [ ] Documentation is updated.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 66.61%. Comparing base (483c5a5) to head (0a5b88c).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #894 +/- ## ========================================== + Coverage 66.59% 66.61% +0.01% ========================================== Files 55 55 Lines 5942 5942 ========================================== + Hits 3957 3958 +1 + Misses 1985 1984 -1 ``` | [Flag](https://app.codecov.io/gh/qiboteam/qibolab/pull/894/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=qiboteam) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/qiboteam/qibolab/pull/894/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=qiboteam) | `66.61% <100.00%> (+0.01%)` | :arrow_up: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=qiboteam#carryforward-flags-in-the-pull-request-comment) to find out more.

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[Edoardo-Pedicillo]

Thanks @alecandido, updating the tests I spotted another typo https://github.com/qiboteam/qibolab/blob/483c5a541f5d8f67f2e561958544aff314a425c6/src/qibolab/backends.py#L128-L131 also here is missing an "s" in circuit.