[Airflow] Remove Airflow < 2.3.0 support

[kacpermuda]

Problem

Airflow < 2.3.0 is not offered by any major cloud provider and OL support for it has some limitations.

Solution

I think we can remove support for any Airflow version below 2.3.0

One-line summary:

Remove Airflow < 2.3.0 support

Checklist

• You've signed-off your work
• Your pull request title follows our guidelines
• Your changes are accompanied by tests (if relevant)
• Your change contains a small diff and is self-contained
• You've updated any relevant documentation (if relevant)
• Your comment includes a one-liner for the changelog about the specific purpose of the change (not required for changes to tests, docs, or CI config)
• You've versioned the core OpenLineage model or facets according to SchemaVer (if relevant)
• You've added a header to source files (if relevant)

---

SPDX-License-Identifier: Apache-2.0
Copyright 2018-2024 contributors to the OpenLineage project

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.49%. Comparing base (6a6008d) to head (360ff0e).
Report is 1 commits behind head on main.

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Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2710      +/-   ##
==========================================
+ Coverage   84.59%   85.49%   +0.90%     
==========================================
  Files          59       58       -1     
  Lines        3446     3405      -41     
==========================================
- Hits         2915     2911       -4     
+ Misses        531      494      -37     

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[mobuchowski]

One doc change, but overall looks good to me.