Remove custom feature category recordings for the puma component

In gitlab-com/runbooks!3241 (merged) we've added custom recordings to use different metrics to record puma-apdex for feature categories then the metrics we were using for the puma component in the web, git and api services.

In gitlab-com/runbooks!4020 (merged) we've added a way to signify that an SLI has a feature category label in it's source metrics, when doing so the source metrics for the SLI would be used to populate the feature category aggregation set.

In #1230 (closed) we've stopped using the puma-apdex SLI in favour of the rails_requests one that includes feature_category, endpoint_id and a configurable urgency.

The http_requests_total that is used for the errors part does have a feature_category label. So we could use the featureCategory: fromSourceMetrics approach to record the error rate and remove the apdex recordings once all of the stage groups have opted in to the rails_requests SLI.