wlr_keyboard: use correct printf format string for keymap_size

keymap_size is a size_t. Otherwise the build fails on arm like

../types/wlr_keyboard.c: In function 'wlr_keyboard_set_keymap':
../include/wlr/util/log.h:34:17: error: format '%lu' expects argument of type 'long unsigned int', but argument 5 has type 'size_t {aka unsigned int}' [-Werror=format=]
  _wlr_log(verb, "[%s:%d] " fmt, _strip_path(__FILE__), __LINE__, ##__VA_ARGS__)
                 ^
../types/wlr_keyboard.c:218:3: note: in expansion of macro 'wlr_log'
   wlr_log(L_ERROR, "creating a keymap file for %lu bytes failed", kb->keymap_size);
   ^~~~~~~
../types/wlr_keyboard.c:218:50: note: format string is defined here
   wlr_log(L_ERROR, "creating a keymap file for %lu bytes failed", kb->keymap_size);
                                                ~~^
                                                %u

0 files changed, 0 insertions, 0 deletions