fix: prevent dropping materialized views on Postgres versions < 9.3

[AlexMesser]

Description of change

Materialized views introduced in Postgres 9.3. This PR adds version check before dropping materialized views to prevent errors on Postgres versions lower than 9.3

Fixes #7714

Pull-Request Checklist

• Code is up-to-date with the master branch
• npm run lint passes with this change
• npm run test passes with this change
• This pull request links relevant issues as Fixes #0000
• There are new or updated unit tests validating the change
• Documentation has been updated to reflect this change
• The new commits follow conventions explained in CONTRIBUTING.md

[imnotjames]

We can probably cache the version but this works anyway.

[imnotjames]

However, I agree with the comment in the related issue:

Postgres 9.2 official support was ended in 2017. We can't keep backward compatibility for all existing database versions.

It'd be easier to update the documentation to just say we require Postgres >= 9.3

[mitsos1os]

Wouldn't it be better if getVersion moved to PostgresDriver, also cache the result as a property in the driver (ex: serverVersion) that could later be used directly in any subsequent scenarios? (ex: #7741)