(CONT-967) Replace all uses of validate_*() with assert_type()

[david22swan]

The process of removing all deprecated functions from stdlib has begun, so we now need to replace all mentions of validate_*() with the built in assert_type() function.

[puppet-community-rangefinder]

wsus_client is a class

that may have no external impact to Forge modules.

wsus_client::setting is a type

that may have no external impact to Forge modules.

This module is declared in 1 of 580 indexed public Puppetfiles.

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