config: cleanup language on readonly parameter

config.md

@@ -21,7 +21,7 @@ Each container has exactly one *root filesystem*, and any number of optional *mo
 
 The path string element specifies the path to the root file system for the container, relative to the path where the manifest is. A directory MUST exist at the relative path declared by the field.
 
-The readonly is an optional boolean element which defaults to false. If it is true, access to the root file system MUST be read-only for all processes running inside it, whether you want the root file system to be readonly or not for the processes running on it.
+The readonly is an optional boolean element which defaults to false. If readonly is true then the root file system MUST be read-only inside the container.
 
 *Example*
 ```json