Unpin pandas-gbq and remove unused code

[kaxil]

BigQueryPandasConnector was previously used by BigqueryHook.get_pandas_df. This was fixed in ad308ea (in 2018). However we forgot to remove BigQueryPandasConnector which is age-old code (2016) and used private methods.

2016 code - https://github.com/apache/airflow/pull/1452/files

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[kaxil]

Single SQLite failure is unrelated

[jedcunningham]

Any backcompat concerns? We can bump the major for the provider easy enough, but not as straight forward with the contrib in core.

[kaxil]

Any backcompat concerns? We can bump the major for the provider easy enough, but not as straight forward with the contrib in core.

Hardly think so, ancient code that doesn't make sense to use in isolation. BigQueryPandasConnector was previously used by BigqueryHook.get_pandas_df. This was fixed in ad308ea (in 2018). However we forgot to remove BigQueryPandasConnector which is age-old code (2016) and used private methods.

So I don'g see any concerns

[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]

Hell yeah :)