[stable/mariadb] Fix typo of the install example in README (#11124)

Signed-off-by: Jungsub Shin <supsup5642@gmail.com>

stable/mariadb/Chart.yaml

@@ -1,5 +1,5 @@
 name: mariadb
-version: 5.5.0
+version: 5.5.1
 appVersion: 10.1.37
 description: Fast, reliable, scalable, and easy to use open-source relational database system. MariaDB Server is intended for mission-critical, heavy-load production systems as well as for embedding into mass-deployed software. Highly available MariaDB cluster.
 keywords:

stable/mariadb/README.md

@@ -141,7 +141,7 @@ Specify each parameter using the `--set key=value[,key=value]` argument to `helm
 
 ```bash
 $ helm install --name my-release \
-  --set root.password=secretpassword,user.database=app_database \
+  --set rootUser.password=secretpassword,db.user=app_database \
     stable/mariadb
 ```