Create Secret / Fixed the raw data example

Based on the description the example is supposed to create a Secret that stores the username  and the password, but this was not the case. It was using the devuser username instead of admin. I have changed the example to be actually doing the task that was described above.

Author: 4TT1L4

content/en/docs/tasks/configmap-secret/managing-secret-using-kubectl.md

@@ -33,7 +33,7 @@ Run the following command:
 
 ```shell
 kubectl create secret generic db-user-pass \
-    --from-literal=username=devuser \
+    --from-literal=username=admin \
     --from-literal=password='S!B\*d$zDsb='
 ```
 You must use single quotes `''` to escape special characters such as `$`, `\`,