Limit paramiko to < 4.0.0 till we remove DSS support

[amoghrajesh]

A new version of paramiko has been released:

< paramiko==3.5.1
---
> paramiko==4.0.0

Due to the paramiko bump, there is an compatibility issue with newer versions of paramiko (4.0+) where DSSKey has been removed for security reasons.

This was causing test failures in test_should_be_importable for providers that depend on the SSH provider.

Failure:

Traceback (most recent call last):
  File "/opt/airflow/airflow-core/src/airflow/models/dagbag.py", line 432, in parse
    loader.exec_module(new_module)
  File "<frozen importlib._bootstrap_external>", line 883, in exec_module
  File "<frozen importlib._bootstrap>", line 241, in _call_with_frames_removed
  File "/opt/airflow/providers/google/tests/system/google/cloud/transfers/example_gcs_to_sftp.py", line 30, in <module>
    from airflow.providers.google.cloud.transfers.gcs_to_sftp import GCSToSFTPOperator
  File "/opt/airflow/providers/google/src/airflow/providers/google/cloud/transfers/gcs_to_sftp.py", line 31, in <module>
    from airflow.providers.sftp.hooks.sftp import SFTPHook
  File "/opt/airflow/providers/sftp/src/airflow/providers/sftp/hooks/sftp.py", line 39, in <module>
    from airflow.providers.ssh.hooks.ssh import SSHHook
  File "/opt/airflow/providers/ssh/src/airflow/providers/ssh/hooks/ssh.py", line 43, in <module>
    class SSHHook(BaseHook):
  File "/opt/airflow/providers/ssh/src/airflow/providers/ssh/hooks/ssh.py", line 81, in SSHHook
    paramiko.DSSKey,

Example: https://github.com/apache/airflow/actions/runs/16713668042/job/47303410955.

An ideal way forward would be to remove the DSS support from airflow & bump the paramiko version with that, for now, to fix CI, i think limiting paramiko to < 4.0.0 would be good enough.

---

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[github-actions]

Backport failed to create: v3-0-test. View the failure log Run details

Status	Branch	Result
❌	v3-0-test

You can attempt to backport this manually by running:

cherry_picker 18d75db v3-0-test

This should apply the commit to the v3-0-test branch and leave the commit in conflict state marking
the files that need manual conflict resolution.

After you have resolved the conflicts, you can continue the backport process by running:

cherry_picker --continue

[ashb]

I've manually cherry-picked this.