Limit colorlog version (6.x is incompatible)

[malthe]

The "color" method seems to have been removed:

  File "/airflow/airflow/utils/log/colored_log.py", line 86, in _color_record_traceback
    self.color(self.log_colors, record.levelname) + record.exc_text + escape_codes['reset']
AttributeError: 'CustomTTYColoredFormatter' object has no attribute 'color'

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[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.