Ensure C23 standard compatibility

[dio-az]

Fixes the following errors when compiling using -std=c23:

ngx_http_vod_module.c:242:5: error: initialization of 'void (*)(ngx_cycle_t *)' from incompatible pointer type 'void (*)(void)'
  242 |     ngx_http_vod_exit_process,
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~

ngx_http_vod_module.c:243:5: error: initialization of 'void (*)(ngx_cycle_t *)' from incompatible pointer type 'void (*)(void)'
  243 |     ngx_http_vod_exit_process,
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~