config-linux: "may" -> "MAY" for supplying linux.devices

The way that the runtime supplies these is "truly optional", as long
as they get supplied.

Signed-off-by: W. Trevor King <[email protected]>

Author: wking

config-linux.md

@@ -110,7 +110,7 @@ Note that the number of mapping entries MAY be limited by the [kernel][user-name
 ## <a name="configLinuxDevices" />Devices
 
 **`devices`** (array of objects, OPTIONAL) lists devices that MUST be available in the container.
-The runtime may supply them however it likes (with [mknod][mknod.2], by bind mounting from the runtime mount namespace, etc.).
+The runtime MAY supply them however it likes (with [`mknod`][mknod.2], by bind mounting from the runtime mount namespace, etc.).
 
 Each entry has the following structure: