docs: upgrade redis to redis:5.0.9

Author: beli68

README.md

@@ -180,7 +180,7 @@ Step 2. Launch a redis container
 ```bash
 docker run --name gitlab-redis -d \
     --volume /srv/docker/gitlab/redis:/var/lib/redis \
-    sameersbn/redis:4.0.9-2
+    redis:5.0.9
 ```
 
 Step 3. Launch the gitlab container
@@ -359,15 +359,15 @@ To illustrate linking with a redis container, we will use the [sameersbn/redis](
 First, lets pull the redis image from the docker index.
 
 ```bash
-docker pull sameersbn/redis:4.0.9-2
+docker pull redis:5.0.9
 ```
 
 Lets start the redis container
 
 ```bash
 docker run --name gitlab-redis -d \
     --volume /srv/docker/gitlab/redis:/var/lib/redis \
-    sameersbn/redis:4.0.9-2
+    redis:5.0.9
 ```
 
 We are now ready to start the GitLab application.