libsmartcols: (samples): fix format truncation warning

libsmartcols: (samples): fix format truncation warning

As this is only an example and the needed memory is not much just
hardcode a large enough number.
The previously computed value was wrong anyways.

libsmartcols/samples/continuous.c: In function 'main':
libsmartcols/samples/continuous.c:110:61: error: '%3d' directive output may be truncated writing between 3 and 11 bytes into a region of size between 0 and 7 [-Werror=format-truncation=]
  110 |                         snprintf(timecell, timecellsz, "%f [%3d%%]", diff,
      |                                                             ^~~
libsmartcols/samples/continuous.c:110:25: note: 'snprintf' output between 11 and 333 bytes into a destination of size 12
  110 |                         snprintf(timecell, timecellsz, "%f [%3d%%]", diff,
      |                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  111 |                                 done ? 100 : (int)(diff / (TIME_PERIOD / 100.0)));
      |                                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
libsmartcols/samples/continuous.c:110:61: error: '%3d' directive output may be truncated writing 3 bytes into a region of size between 0 and 7 [-Werror=format-truncation=]
  110 |                         snprintf(timecell, timecellsz, "%f [%3d%%]", diff,
      |                                                             ^~~
libsmartcols/samples/continuous.c:110:25: note: 'snprintf' output between 11 and 325 bytes into a destination of size 12
  110 |                         snprintf(timecell, timecellsz, "%f [%3d%%]", diff,
      |                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  111 |                                 done ? 100 : (int)(diff / (TIME_PERIOD / 100.0)));
      |                                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Signed-off-by: Thomas Weißschuh <thomas@t-8ch.de>