Remove Obsolete #ifdefs from the examples

[mehmetyusufoglu]

There were obsolete if defined clauses at the beginning of main() functions of 9 examples, they are removed by this MR. It is never triggered because ALPAKA_ACC_CPU_B_SEQ_T_SEQ_ENABLED always on at CI.

-// Fallback for the CI with disabled sequential backend
-#if defined(ALPAKA_CI) && !defined(ALPAKA_ACC_CPU_B_SEQ_T_SEQ_ENABLED)
-    return EXIT_SUCCESS;
-#else
...
...
#endif