Delete the Lua Dark Harvest acceleration

Same shape as Carnage, opposite direction: Dark Harvest is a channel that makes
the caster's DoTs on the target tick 30% faster, and the server never tells an
observer the remaining durations changed. So this addon stamped dhStartTime on
every tracked record when the channel began, dhEndTime when it stopped, and
subtracted 30% of the elapsed window from each remaining time on read.

ClassicAPI compresses the ticks in the DLL (src/turtle/DarkHarvest.cpp), so
expirationTime already reflects it.

Removed: GetDarkHarvestReduction, ApplyDarkHarvestStart, ApplyDarkHarvestEnd,
GetTimeRemainingWithDarkHarvest, the channel-start capture on both the
UNIT_CASTEVENT and nampower paths, the channel-stop finalizer in
SPELLCAST_CHANNEL_STOP, the darkHarvestData state, and DarkHarvestSpellIDs.

The darkHarvest flag in Extensions/CursiveCustomSpells.lua stays -- that is
spell metadata this addon exports to Cursive, not tracking of our own.

ComboPointTracker.lua

@@ -145,14 +145,6 @@ CleveRoids.ImmolateSpellIDs = {
     [25309] = true,  -- Rank 8
 }
 
--- =============================================================================
--- WARLOCK: Dark Harvest Duration Acceleration (TWoW Custom)
--- Channeled spell that accelerates DoT tick rate by 30% while channeling
--- Complex tracking: debuff expires 30% faster while Dark Harvest is active
--- =============================================================================
--- TWoW custom (see MoltenBlast note).
-CleveRoids.DarkHarvestSpellIDs = RankSet(52550)
-
 -- =============================================================================
 -- DRUID: Rake Debuff Cap Boss Whitelist
 -- These bosses are likely to hit the 48 debuff cap, causing Rake to get pushed off