Fix existing loop-contracts side-effect tests

Author: qinheping

regression/contracts-dfcc/variant_function_call_fail/test.desc

@@ -1,8 +1,8 @@
 CORE
 main.c
 --dfcc main --apply-loop-contracts
-^Decreases clause is not side-effect free. \(at: file main.c line .* function main\)$
-^EXIT=70$
+^Decreases clause is not side-effect free.$
+^EXIT=6$
 ^SIGNAL=0$
 --
 --

regression/contracts-dfcc/variant_side_effects_fail/test.desc

@@ -1,8 +1,8 @@
 CORE
 main.c
 --dfcc main --apply-loop-contracts
-^Decreases clause is not side-effect free. \(at: file main.c line .* function main\)$
-^EXIT=70$
+^Decreases clause is not side-effect free.$
+^EXIT=6$
 ^SIGNAL=0$
 --
 --