sample glib: remove an unmaintainable test

It causes the following warning:

    In file included from ../../cutter/cut-assertions.h:23:0,
                     from ../../cutter/cutter.h:26,
                     from regex.c:21:
    regex.c: In function 'test_split':
    ../../cutter/cut-assertions-helper.h:43:5: warning: 'cut_previous_jump_buffer' may be used uninitialized in this function [-Wmaybe-uninitialized]
         cut_test_context_set_jump_buffer(cut_get_current_test_context(),    \
         ^
    In file included from ../../cutter/cutter.h:28:0,
                     from regex.c:21:
    ../../cutter/cut-assertions-helper.h:32:14: note: 'cut_previous_jump_buffer' was declared here
         jmp_buf *cut_previous_jump_buffer;                                  \
                  ^
    ../../cutter/cut-helper.h:394:9: note: in definition of macro 'cut_trace_with_info_expression'
             expression;                                                     \
             ^
    ../../cutter/cut-assertions.h:231:9: note: in expansion of macro 'cut_test_with_user_message'
             cut_test_with_user_message(                             \
             ^
    regex.c:1193:5: note: in expansion of macro 'cut_assert_equal_int'
         cut_assert_equal_int (g_strv_length (expected), token_count); \
         ^
    regex.c:1222:3: note: in expansion of macro 'TEST_SPLIT'
       TEST_SPLIT("a", "", 0, 1, expected1);
       ^
    ../../cutter/cut-helper.h:396:5: warning: '_cut_test_context' may be used uninitialized in this function [-Wmaybe-uninitialized]
         cut_test_context_pop_backtrace(_cut_test_context);                  \
         ^
    ../../cutter/cut-helper.h:385:21: note: '_cut_test_context' was declared here
         CutTestContext *_cut_test_context;                                  \
                         ^
    ../../cutter/cut-assertions.h:230:5: note: in expansion of macro 'cut_trace_with_info_expression'
         cut_trace_with_info_expression(                             \
         ^
    regex.c:1193:5: note: in expansion of macro 'cut_assert_equal_int'
         cut_assert_equal_int (g_strv_length (expected), token_count); \
         ^
    regex.c:1222:3: note: in expansion of macro 'TEST_SPLIT'
       TEST_SPLIT("a", "", 0, 1, expected1);
       ^

But we can't fix it with simple and fuss-free way.