Remove (wrong) primitive usage

[guillep]

Fix #16775
Fix hpi-swa/smalltalkCI#646 (comment)

Primitive 231 was never implemented on the VM, or at least not since a Loooong time.
See https://github.com/pharo-project/pharo-vm/compare/v10.0.5...v10.2.1

(231 239 primitiveFail)

And recently it got defined to provide an object's format:

(231 primitiveFormat)

However, it is used in the Random class, probably a leftover of some prototype.

"On Pharo"
Random class >> primitiveRandomNumber: stateArray
	"Answer a random Float in the interval [0 to 1)."

	<primitive: 231>
...

I'll propose a PR, just removing the primitive tag in primitiveRandomNumber: should be enough to get back the old behavior. We should also back port it to P12.