brlapi_server: Do not look at parameters when freeing a tty
brlapi_server: Do not look at parameters when freeing a tty

Ttys do not have parameter subscriptions, and locking apiParamMutex
would bring an unwanted apiConnectionsMutex -> apiParamMutex lock
ordering.

brltty/brltty,brltty/brltty,brltty/brltty,brltty/brltty,brltty/brltty,brltty/brltty