0.2: Replace "non-falsifiable" with a more accurate term

[MarkLodato]

The term non-falsifiable is used incorrectly in the SLSA requirements. "Falsifiable" means that a theory can be proved false though some test, which is actually a good thing. What we actually mean is "non-forgeable," though perhaps there is an even better term. Any suggestions? (Note: This is also somewhat related to #261.)

I suggest that we wait until v0.2 to change the term, since doing so will break existing references.

[MarkLodato]

Once it's decided to change, we could add a note to v0.1 noting this misuse of the term.

[david-a-wheeler]

For 0.1 we can add a note, but for version 0.2 let's definitely switch to the correct term :-).

[david-a-wheeler]

The scientific meaning of falsifiable is "capable of being disproved through experiment". The meaning intended here is "incapable of being undetectably false", which is a plausible meaning of the word but isn't what will come to mind to many.

Perhaps "non-forgeable" or "verifiable" are better terms?

[trishankatdatadog]

Thoughts @cedricvanrompay-datadog?

[MarkLodato]

Let's merge this into #306 so that we have a single "terminology" issue rather than one per term.