fix: warning '-Wstringop-truncation' with GCC 11.2

fix: warning '-Wstringop-truncation' with GCC 11.2

Building with GCC 11.2 results in the following warning :

  In file included from ../../src/common/tracker.h:18,
                 from ../../src/bin/lttng-sessiond/trace-ust.h:17,
                 from test_ust_data.cpp:19:
../../src/common/sessiond-comm/sessiond-comm.h:569:14: note: while referencing ‘lttng_event_exclusion::names’
  569 |         char names[0][LTTNG_SYMBOL_NAME_LEN];
      |              ^~~~~
test_ust_data.cpp:209:16: warning: ‘char* strncpy(char*, const char*, size_t)’ specified bound 256 equals destination size [-Wstringop-truncation]
  209 |         strncpy(LTTNG_EVENT_EXCLUSION_NAME_AT(exclusion, 0),
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  210 |                 get_random_string(), LTTNG_SYMBOL_NAME_LEN);
      |                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
test_ust_data.cpp:211:16: warning: ‘char* strncpy(char*, const char*, size_t)’ specified bound 256 equals destination size [-Wstringop-truncation]
  211 |         strncpy(LTTNG_EVENT_EXCLUSION_NAME_AT(exclusion, 1),
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  212 |                 get_random_string(), LTTNG_SYMBOL_NAME_LEN);
      |                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Change-Id: I78eea760b4684227ee457c3368c6397d0a767af5
Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>