Make internal event cli rspec examples consistent with recommended ruby code

When using the Gitlab::InternalEventsTracking module as recommended for instrumenting internal events, the default category value is the class name.

When using the 'internal event tracking' shared example, the default value for category is 'InternalEventTracking' (for maintaining legacy support). But we should recommend using the expected category for new usages of the shared example. This MR updates the internal events cli to include that in the generated output.