c/pthread-lit: fix verdict of two benchmarks, probably an oversight in !1414

The two benchmarks

• pthread-lit/sssc12-2
• pthread-lit/sssc12_variant-2

which were added in MR !1414 (merged) as original sources after fixing an overflow bug with them, still have the wrong verdict: valid-deref true.

As the overflow issue in these copies of the original unfixed benchmarks is still present, the verdict should be false.