tests: os: swap: increase wiggle room in swap check

[rcooke-warwick]

We encountered the variance in expected and measured swap in the rpi5 to be higher than the allowed value of 10 - to make this safe and allowing of more device types, changed the allowed variation - still small enough to actually check the value is right, but should reduce false negatives

required to unblock raspberrypi5 work
https://balena.fibery.io/search/Yc6vY#Work/Project/Support-new-raspberry-Pi-CM5-device-type-949

Change-type: patch

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