Bug in ExpectQueriedColumnValueFrequencyToMeetThreshold

[ilinardic22]

Hello,

I was trying to use an experimental expectation:
https://github.com/great-expectations/great_expectations/blob/develop/contrib/experimental/great_expectations_experimental/expectations/expect_queried_column_value_frequency_to_meet_threshold.py

When I used it, I got the following error: great_expectations.exceptions.exceptions.MetricResolutionError: (psycopg2.errors.SyntaxError) subquery in FROM must have an alias.

I resolved the error by adding the aliases after the subqueries in FROM statements. I was not sure should I raise a pull request about this or open a discussion so I opted for the second option.

If you would like me to also raise a pull request about it, I would be happy to do so.