Remove rubocop `CodeReuse/ServiceClass`

What does this MR do?

The CodeReuse/ServiceClass cop was previously disabled because the Integrations::Jira model used to be named PrometheusService, which triggered the cop.

The model was renamed in !61743 (merged) however it was missed that we could remove this pragma comment until it was raised by @cablett in !62645 (comment 602285858).

Does this MR meet the acceptance criteria?

Conformity

• [-] I have included changelog trailers, or none are needed. (Does this MR need a changelog?)
• [-] I have added/updated documentation, or it's not needed. (Is documentation required?)
• [-] I have properly separated EE content from FOSS, or this MR is FOSS only. (Where should EE code go?)
• [-] I have added information for database reviewers in the MR description, or it's not needed. (Does this MR have database related changes?)
• I have self-reviewed this MR per code review guidelines.
• This MR does not harm performance, or I have asked a reviewer to help assess the performance impact. (Merge request performance guidelines)
• I have followed the style guides.
• This change is backwards compatible across updates, or this does not apply.