Fix `IO_Event_Selector_EPoll` -> `KQueue` typo.

[ioquatix]

Not sure how this was compiling but it was.

./io/event/selector/kqueue.c:374:2: warning: incompatible pointer types assigning to 'struct IO_Event_Selector_KQueue *' from 'struct IO_Event_Selector_EPoll *' [-Wincompatible-pointer-types]
        TypedData_Get_Struct(self, struct IO_Event_Selector_EPoll, &IO_Event_Selector_KQueue_Type, selector);
        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/Users/samuel/.rubies/ruby-3.3.0/include/ruby-3.3.0/ruby/internal/core/rtypeddata.h:516:13: note: expanded from macro 'TypedData_Get_Struct'
    ((sval) = RBIMPL_CAST((type *)rb_check_typeddata((obj), (data_type))))
            ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Types of Changes

• Bug fix.

Contribution

• [ ] I added tests for my changes.
• [x] I tested my changes locally.
• [x] I agree to the Developer's Certificate of Origin 1.1.