Correct spelling etc in pack and unpack array routines

[codecov[bot]]

Codecov Report

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

Project coverage is 89.63%. Comparing base (829497d) to head (b6b32f6).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #2955 +/- ## ======================================= Coverage 89.63% 89.63% ======================================= Files 29 29 Lines 30176 30176 Branches 5877 5877 ======================================= Hits 27047 27047 Misses 1790 1790 Partials 1339 1339 ``` | [Flag](https://app.codecov.io/gh/tskit-dev/tskit/pull/2955/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=tskit-dev) | Coverage Δ | | |---|---|---| | [c-tests](https://app.codecov.io/gh/tskit-dev/tskit/pull/2955/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=tskit-dev) | `86.20% <ø> (ø)` | | | [lwt-tests](https://app.codecov.io/gh/tskit-dev/tskit/pull/2955/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=tskit-dev) | `80.78% <ø> (ø)` | | | [python-c-tests](https://app.codecov.io/gh/tskit-dev/tskit/pull/2955/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=tskit-dev) | `88.72% <ø> (ø)` | | | [python-tests](https://app.codecov.io/gh/tskit-dev/tskit/pull/2955/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=tskit-dev) | `99.01% <ø> (ø)` | | 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=tskit-dev#carryforward-flags-in-the-pull-request-comment) to find out more. | [Files](https://app.codecov.io/gh/tskit-dev/tskit/pull/2955?dropdown=coverage&src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=tskit-dev) | Coverage Δ | | |---|---|---| | [python/tskit/util.py](https://app.codecov.io/gh/tskit-dev/tskit/pull/2955?src=pr&el=tree&filepath=python%2Ftskit%2Futil.py&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=tskit-dev#diff-cHl0aG9uL3Rza2l0L3V0aWwucHk=) | `100.00% <ø> (ø)` | |

[benjeffery]

@mergifyio rebase

[mergify[bot]]

rebase

✅ Branch has been successfully rebased