Fix fixmes for variadics

[fredemmott]

/* HH_FIXME[4033] variadic params with type constraints are not supported */

Given that 3.12 support has been dropoped, these can all be cleaned up

[simonwelsh]

hh_client --remove-dead-fixmes will do this for you

[fredemmott]

TIL, thanks - though still lots of manual work because:

• Was expecting a type hint (what about: array) (Typing[4033])
• . Invalid return type (Typing[4110])

[fredemmott]

:/ This didn't actually find them all, weird.