Doc: distributed reads enabled by default

As performance issue https://gitlab.com/gitlab-org/gitaly/-/merge_requests/2372 with database
query has been fixed. The feature is switched to be enabled
by default, but still remains under control of the feature flag.
It could be disabled by disabling a feature flag in console.

Relates to: https://gitlab.com/gitlab-org/gitaly/-/issues/2951

doc/administration/gitaly/praefect.md

@@ -940,19 +940,14 @@ cluster.
 
 ## Distributed reads
 
-> Introduced in GitLab 13.1 in [beta](https://about.gitlab.com/handbook/product/gitlab-the-product/#alpha-beta-ga) with feature flag `gitaly_distributed_reads` set to disabled.
-
 Praefect supports distribution of read operations across Gitaly nodes that are
 configured for the virtual node.
 
-To allow for [performance testing](https://gitlab.com/gitlab-org/quality/performance/-/issues/231),
-distributed reads are currently in
-[beta](https://about.gitlab.com/handbook/product/gitlab-the-product/#alpha-beta-ga) and disabled by
-default. To enable distributed reads, the `gitaly_distributed_reads`
-[feature flag](../feature_flags.md) must be enabled in a Ruby console:
+The feature is enabled by default. To disable distributed reads, the `gitaly_distributed_reads`
+[feature flag](../feature_flags.md) must be disabled in a Ruby console:
 
 ```ruby
-Feature.enable(:gitaly_distributed_reads)
+Feature.disable(:gitaly_distributed_reads)
 ```
 
 If enabled, all RPCs marked with `ACCESSOR` option like