Fix deprecated interface for YAML.safe_load

What does this MR do and why?

Passing in the permitted classes as the second argument was deprecated in Psych 3 (https://github.com/ruby/psych/pull/378) and removed in Psych 4 (https://github.com/ruby/psych/pull/487).

Ruby 3.1 ships with Psych 4, so to make the code work for Ruby 2.7 and up, use the permitted_classes keyword argument.

Part of #396231 (closed)

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