Change name of TestClass in 2 spec files

What does this MR do?

Since qualified_domain_array_validator_spec.rb and spec/models/concerns/safe_url_spec.rb used the same name for a Class (TestClass), they caused order dependent spec failures like https://gitlab.com/gitlab-org/gitlab/-/jobs/383000878

The minimal command to reproduce the spec failures on local is:

rspec -fd ./spec/validators/qualified_domain_array_validator_spec.rb[1:1:1:1,1:1:3] ./spec/models/concerns/safe_url_spec.rb[1:1:1]

This MR renames the TestClass in both specs.

Issue: #118833 (closed)

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