remove `vec:Vector` of the PartitionedVector

[codecov[bot]]

Codecov Report

Base: 98.97% // Head: 98.96% // Decreases project coverage by -0.01% :warning:

Coverage data is based on head (144a2b4) compared to base (2791818). Patch coverage: 100.00% of modified lines in pull request are covered.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #12 +/- ## ========================================== - Coverage 98.97% 98.96% -0.02% ========================================== Files 6 6 Lines 195 193 -2 ========================================== - Hits 193 191 -2 Misses 2 2 ``` | [Impacted Files](https://codecov.io/gh/paraynaud/PartitionedVectors.jl/pull/12?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Paul+Raynaud) | Coverage Δ | | |---|---|---| | [src/base.jl](https://codecov.io/gh/paraynaud/PartitionedVectors.jl/pull/12/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Paul+Raynaud#diff-c3JjL2Jhc2Uuamw=) | `98.11% <ø> (ø)` | | | [src/struct.jl](https://codecov.io/gh/paraynaud/PartitionedVectors.jl/pull/12/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Paul+Raynaud#diff-c3JjL3N0cnVjdC5qbA==) | `100.00% <100.00%> (ø)` | | Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Paul+Raynaud). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Paul+Raynaud)

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