Make ignore_fields_for_comparison context manager importable

[JSCU-CNI]

The ignore_fields_for_comparison context manager is currently not importable directly from flow.record. The small fix in this PR enables the following usage:

from flow.record import ignore_fields_for_comparison

with ignore_fields_for_comparison([...]):

[codecov[bot]]

Codecov Report

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

Project coverage is 83.76%. Comparing base (80c8918) to head (a00bb56).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #126 +/- ## ======================================= Coverage 83.76% 83.76% ======================================= Files 34 34 Lines 3413 3413 ======================================= Hits 2859 2859 Misses 554 554 ``` | [Flag](https://app.codecov.io/gh/fox-it/flow.record/pull/126/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=fox-it) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/fox-it/flow.record/pull/126/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=fox-it) | `83.76% <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=fox-it#carryforward-flags-in-the-pull-request-comment) to find out more.

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