Revert "Add FORK_CHILD_PRE / FORK_CHILD_CANCELLED subevents (#90)"

[gabsow]

Reverts #90 ("Add FORK_CHILD_PRE / FORK_CHILD_CANCELLED subevents").

Companion to the core revert redis/redis#15432, which removes the FORK_CHILD_PRE / FORK_CHILD_CANCELLED subevents from Redis. This redismodule.h is a vendored copy of core's header, so it must track that revert — otherwise the SDK header would advertise two subevents that core no longer defines.

Why

The pre-fork module-coordination subevents are being reverted in core: as implemented they don't let a module actually refuse/delay a fork (no real handshake), the only deadlock they targeted is AddressSanitizer-specific (guarded in production by the allocator's own pthread_atfork), and there is no consumer going ahead with the approach. See redis/redis#15432 for the full rationale.

Change

• Reverts the single redismodule.h change from Add FORK_CHILD_PRE / FORK_CHILD_CANCELLED subevents #90.
• REDISMODULE_SUBEVENT_FORK_CHILD_* returns to BORN=0, DIED=1, _NEXT=2 — identical to what Revert "Add FORK_CHILD_PRE/CANCELLED subevents for pre-fork module coordination (#15327)" redis/redis#15432 leaves in core's redismodule.h.
• Verified: no remaining references to FORK_CHILD_PRE / FORK_CHILD_CANCELLED.

Should land together with (or after) redis/redis#15432 so the SDK header stays in sync with core.

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Note

Low Risk
Header-only constant removal with no runtime logic; low risk if shipped alongside the matching Redis core revert.

Overview
Reverts the vendored redismodule.h fork-child subevent definitions so they match redis/redis#15432, which drops the pre-fork coordination subevents from core.

REDISMODULE_SUBEVENT_FORK_CHILD_PRE and REDISMODULE_SUBEVENT_FORK_CHILD_CANCELLED are removed; REDISMODULE_SUBEVENT_FORK_CHILD_* is back to BORN=0, DIED=1, and _NEXT=2 only. The SDK header no longer advertises subevents that Redis will not emit.

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