Update existing test to add correct z3 arguments

So that the z3 sub process is actually started and expecting smt2
commands from the pipe in this test.

Author: thomasspriggs

regression/cbmc-incr-smt2/nondeterministic-int-assert/incremental_solver_called.desc

@@ -1,7 +1,7 @@
 CORE
 test.c
---incremental-smt2-solver z3
-Passing problem to incremental SMT2 solving via "z3"
+--incremental-smt2-solver "z3 --smt2 -in"
+Passing problem to incremental SMT2 solving via "z3 --smt2 -in"
 ^EXIT=(0|127|134|137)$
 ^SIGNAL=0$
 identifier: main::1::x