Tests: Fix decision-procedure-runtime pattern

In
https://github.com/diffblue/cbmc/actions/runs/4398169028/jobs/7701816018
we saw a runtime of 9e-05s, i.e., no fractional part was printed for it
was zero.

Author: tautschnig

regression/cbmc/Failing_Assert1/dimacs.desc

@@ -1,7 +1,7 @@
 CORE
 main.c
 --dimacs
-^Runtime decision procedure: [0-9]+(\.[0-9]+(e-[0-9]+)?)?s$
+^Runtime decision procedure: [0-9]+(\.[0-9]+)?(e-[0-9]+)?s$
 ^c main::1::i!0@1#1
 ^c main::1::j!0@1#1
 ^EXIT=0$

regression/cbmc/Failing_Assert1/test.desc

@@ -4,6 +4,6 @@ main.c
 ^EXIT=10$
 ^SIGNAL=0$
 ^VERIFICATION FAILED$
-^Runtime decision procedure: [0-9]+(\.[0-9]+(e-[0-9]+)?)?s$
+^Runtime decision procedure: [0-9]+(\.[0-9]+)?(e-[0-9]+)?s$
 --
 ^warning: ignoring