Disabling of reads distribution feature

Feature flag 'distributed_reads' is disabled by default.
The documentation mentions issue why that needed and how to
enable it for usage.

Related to: https://gitlab.com/gitlab-org/gitaly/-/issues/3178

doc/administration/gitaly/praefect.md

@@ -943,16 +943,17 @@ 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.
-> - [Made generally available](https://gitlab.com/gitlab-org/gitaly/-/issues/2951) in GitLab 13.3.
+> - [Made generally available and enabled by default](https://gitlab.com/gitlab-org/gitaly/-/issues/2951) in GitLab 13.3.
+> - [Disabled by default](https://gitlab.com/gitlab-org/gitaly/-/issues/3178) in GitLab 13.5.
 
 Praefect supports distribution of read operations across Gitaly nodes that are
 configured for the virtual node.
 
-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:
+The feature is disabled by default. To enable distributed reads, the `gitaly_distributed_reads`
+[feature flag](../feature_flags.md) must be enabled in a Ruby console:
 
 ```ruby
-Feature.disable(:gitaly_distributed_reads)
+Feature.enable(:gitaly_distributed_reads)
 ```
 
 If enabled, all RPCs marked with `ACCESSOR` option like