renamed fs_type to type for volumes

Change-Id: I876c9462a2625453e88488b8407af4ea25e77ae0
diff --git a/README.rst b/README.rst
index 4382320..f8ef542 100644
--- a/README.rst
+++ b/README.rst
@@ -255,11 +255,11 @@
                 volume:
                   tmp:
                     size: 5G
-                    fs_type: ext4
+                    type: ext4
                     mount: '/tmp'
                   log:
                     size: 7G
-                    fs_type: ext4
+                    type: ext4
                     mount: '/var/log'
 
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