OPT: remove `RootModel` where it is unnecessary

[codecov[bot]]

Codecov Report

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

Comparison is base (8df4f55) 91.34% compared to head (0ac0c1d) 91.34%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #82 +/- ## ======================================= Coverage 91.34% 91.34% ======================================= Files 30 30 Lines 763 763 Branches 93 93 ======================================= Hits 697 697 Misses 47 47 Partials 19 19 ``` | [Files](https://app.codecov.io/gh/kpn/combadge/pull/82?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=kpn) | Coverage Δ | | |---|---|---| | [combadge/support/zeep/backends/base.py](https://app.codecov.io/gh/kpn/combadge/pull/82?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=kpn#diff-Y29tYmFkZ2Uvc3VwcG9ydC96ZWVwL2JhY2tlbmRzL2Jhc2UucHk=) | `91.66% <100.00%> (ø)` | |

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