Remove prometheus_metrics_transaction_allocated_memory flag

doc/administration/monitoring/prometheus/gitlab_metrics.md

@@ -90,7 +90,6 @@ The following metrics can be controlled by feature flags:
 | Metric                                                         | Feature Flag                                                       |
 |:---------------------------------------------------------------|:-------------------------------------------------------------------|
 | `gitlab_method_call_duration_seconds`                          | `prometheus_metrics_method_instrumentation`                        |
-| `gitlab_transaction_allocated_memory_bytes`                    | `prometheus_metrics_transaction_allocated_memory`                  |
 | `gitlab_view_rendering_duration_seconds`                       | `prometheus_metrics_view_instrumentation`                          |
 
 ## Sidekiq Metrics available for Geo **(PREMIUM)**

lib/gitlab/metrics/transaction.rb

@@ -164,7 +164,6 @@ module Gitlab
         docstring 'Transaction allocated memory bytes'
         base_labels BASE_LABELS
         buckets [100, 1000, 10000, 100000, 1000000, 10000000]
-        with_feature :prometheus_metrics_transaction_allocated_memory
       end
 
       def self.transaction_metric(name, type, prefix: nil, tags: {})