Update hex reference

[daobrien]

https://stylepedia.net/style/#quotation-marks

In the program segment, ensure that the value is X'FF'.

Update the reference to a hex value to 0xFF.

In fact, given that this section is about the use of quotation marks, we need a new example, because specifying hex values doesn't use quotes at all, except perhaps in some special circumstance(?).

[julian-cable]

Given that this example is one of five examples, I propose to remove it, and the other examples should suffice.