Remove markdown from core dependencies

[Taragolis]

I can't find any reference to markdown in Airflow codebase

❯ grep -inr --include \*.py 'from markdown ' airflow

❯ grep -inr --include \*.py 'import markdown ' airflow

❯ grep -inr --include \*.py 'import markdown' airflow
airflow/www/utils.py:34:from markdown_it import MarkdownIt

❯ grep -inr --include \*.py 'from markdown' airflow
airflow/www/utils.py:34:from markdown_it import MarkdownI

Seems like it is stale dependencies from time when we switch to markdown-it-py library: #19702

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[Taragolis]

I guess it should be remaining in constraints, because markdown is dependency for apprise which is dependency for apache-airflow-providers-apprise

[potiuk]

I guess it should be remaining in constraints, because markdown is dependency for apprise which is dependency for apache-airflow-providers-apprise

Ah yeah - then there is no need to change EPOCH, this will also be nicer for the cache if we do not change it.