Revert cascading truncations

[blakethepatton]

This PR reverses #26389 which introduces cascading truncations in postgres. The spirit of the original fix was to address a constraint of postgres in that disabling foreign key constrains does not allow a developer to a truncate a table that has foreign keys. However, the proposed and accepted solution results in all tables that have a column that references the table under question for truncation to be also truncated and further any tables that referenced the children of the first table. This can and has created a problematic situation when you discover that truncating a small table results in the loss of your entire database.

As that is not expected behavior for truncation of a table, I would propose that the word cascading be removed from truncation and that documentation be created in the laravel docs indicating that this was the behavior in postgres between version [initial release version] and [this release version].

Issue: #29506

[GrahamCampbell]

Please send to 6.x only.