Remove incorrect type comment in Swagger2Specification._set_defaults classmethod

[brain-buster]

related: #19006

[brain-buster]

@uranusjr Please, can you help me with this PR? I don't understand why one of the checks was failed ((

[uranusjr]

Don't worry about that, it's unrelated and will be fixed separately.

[uranusjr]

Not sure what the policy of updating things in _vendor is though, waiting for someone who does to do the merge.

[github-actions]

The PR most likely needs to run full matrix of tests because it modifies parts of the core of Airflow. However, committers might decide to merge it quickly and take the risk. If they don't merge it quickly - please rebase it to the latest main at your convenience, or amend the last commit of the PR, and push it with --force-with-lease.

[potiuk]

We usually don't chenge vendored code. We could potentially exclude the connexion package from mypy checks but (from what I understand) in this case it is not "airflow's" mypy that fails but the problem is that if the user want to check their own DAG that imports airflow. It would be a bit too much to require from our users to exclude the package with their mypy checks, and since the fix is simple (and without any runtime code change), and the same fix is already done in upstream, I see no reason why we should not merge it.

[potiuk]

CC: @jedcunningham - if there is still time - might be good to cherry-pick that one to 2.2.1 - it's 0-risk change that solves real issue of the users.

[potiuk]

@jedcunningham - I cherry-picked it now to v2-2-test