Remove extra postgres dependency from AWS Provider

[mariotaddeucci]

Removed postgres provider specific versions dependency generated on #18027 (more details on #18671).
Using the RedshiftSQLHook introduced on #18447 and replicating the method get_table_primary_key to it.
The get_table_primary_key wasn't removed from PostgresHook because can be used on it.

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[uranusjr]

Re-triggering CI.

[potiuk]

This one needs also similar change in redshift_to_s3 and example dags @mariotaddeucci . Once you do it, you will see that the dependency betwen S3 and Postgres will be automatically removed (by pre-commit) from https://github.com/apache/airflow/blob/main/airflow/providers/dependencies.json (this is where we take cross-provider dependencies when we generate setup.py for providers).

Only then the [postgres] extra will actually disappear from amazon provider.

[github-actions]

The PR is likely OK to be merged with just subset of tests for default Python and Database versions without running the full matrix of tests, because it does not modify the core of Airflow. If the committers decide that the full tests matrix is needed, they will add the label 'full tests needed'. Then you should rebase to the latest main or amend the last commit of the PR, and push it with --force-with-lease.