computeinfo: fix memory leak (#2002)

Even on the common code path (i.e., no error paths taken),
test_computeinfo failed to release its allocated memory, preventing a
clean run with LeakSanitizer.

Signed-off-by: Sven van Haastregt <sven.vanhaastregt@arm.com>

test_conformance/computeinfo/main.cpp

@@ -1452,5 +1452,9 @@ int main(int argc, const char** argv)
         }
     }
 
-    return runTestHarness(argCount, argList, test_num, test_list, true, 0);
+    int error = runTestHarness(argCount, argList, test_num, test_list, true, 0);
+
+    free(argList);
+
+    return error;
 }