Docs: Put back deleted HA images

doc/administration/high_availability/README.md

@@ -135,7 +135,7 @@ the contention.
 - 2 or more GitLab application nodes (Unicorn, Workhorse, Sidekiq, PGBouncer)
 - 1 NFS/Gitaly server
 
-![Horizontal architecture diagram](https://docs.gitlab.com/ee/administration/img/high_availability/horizontal.png)
+![Horizontal architecture diagram](img/horizontal.png)
 
 ### Hybrid
 
@@ -153,7 +153,7 @@ contention due to certain workloads.
 - 1 or more NFS/Gitaly servers
 - 1 Monitoring node (Prometheus, Grafana)
 
-![Hybrid architecture diagram](https://docs.gitlab.com/ee/administration/img/high_availability/hybrid.png)
+![Hybrid architecture diagram](img/hybrid.png)
 
 #### Reference Architecture
 
@@ -194,7 +194,7 @@ with the added complexity of many more nodes to configure, manage and monitor.
 - 2 or more Web nodes (All other web requests)
 - 2 or more NFS/Gitaly servers
 
-![Fully Distributed architecture diagram](https://docs.gitlab.com/ee/administration/img/high_availability/fully-distributed.png)
+![Fully Distributed architecture diagram](img/fully-distributed.png)
 
 The following pages outline the steps necessary to configure each component
 separately:

doc/administration/high_availability/database.md

@@ -134,7 +134,7 @@ otherwise the networks will become a single point of failure.
 
 #### Architecture
 
-![PG HA Architecture](pg_ha_architecture.png)
+![PG HA Architecture](img/pg_ha_architecture.png)
 
 Database nodes run two services with PostgreSQL: