lib: bump filter CLI XPath buffers size

lib: bump filter CLI XPath buffers size

Bump the size of the buffers so the new compilers don't complain about
possible truncation:
```
lib/filter_cli.c: In function ‘ipv6_prefix_list_magic.isra.0’:
lib/filter_cli.c:1336:5: error: ‘%lld’ directive output may be truncated writing between 1 and 20 bytes into a region of size between 16 and 527 [-Werror=format-truncation=]
 1336 |     "%s/entry[sequence='%" PRId64 "']", xpath, sseq);
      |     ^~~~~~~~~~~~~~~~~~~~~~
lib/filter_cli.c:1336:25: note: format string is defined here
 1336 |     "%s/entry[sequence='%" PRId64 "']", xpath, sseq);
lib/filter_cli.c:1336:5: note: directive argument in the range [-9223372036854775803, 9223372036854775807]
 1336 |     "%s/entry[sequence='%" PRId64 "']", xpath, sseq);
      |     ^~~~~~~~~~~~~~~~~~~~~~
```

Signed-off-by: Rafael Zalamena <rzalamena@opensourcerouting.org>