fix(examples/templates/docker): persist /home/coder instead of /home/${local.user} (#16190)

Backport of #16189, which is a fix for #16188

examples/templates/docker/main.tf

@@ -184,7 +184,7 @@ resource "docker_container" "workspace" {
     ip   = "host-gateway"
   }
   volumes {
-    container_path = "/home/${local.username}"
+    container_path = "/home/coder"
     volume_name    = docker_volume.home_volume.name
     read_only      = false
   }