[p3lim]

This is how I do it:

local function OrigProviderOnRemoved(self, mapCanvas)
    -- temporary fix to prevent error when removing the original world quest provider, I've notified
    -- Blizzard developers directly about this issue and it should be resolved soon™
    local Map = self:GetMap()
    Map:UnregisterCallback('SetFocusedQuestID', self.setFocusedQuestIDCallback)
    Map:UnregisterCallback('ClearFocusedQuestID', self.clearFocusedQuestIDCallback)
    Map:UnregisterCallback('SetBountyQuestID', self.setBountyQuestIDCallback)
 
    MapCanvasDataProviderMixin.OnRemoved(self, mapCanvas)
end
 
for provider in next, WorldMapFrame.dataProviders do
    if(provider.GetPinTemplate and provider.GetPinTemplate() == 'WorldMap_WorldQuestPinTemplate') then
        -- BUG: the OnRemoved method is broken, so we replace it before we remove the provider
        provider.OnRemoved = OrigProviderOnRemoved
        WorldMapFrame:RemoveDataProvider(provider)
    end
end

The reason I overwrite OnRemoved is because of a bug with the order of execution within it.
Whenever that is fixed, you can just do this:

for provider in next, WorldMapFrame.dataProviders do
    if(provider.GetPinTemplate and provider.GetPinTemplate() == 'WorldMap_WorldQuestPinTemplate') then
        WorldMapFrame:RemoveDataProvider(provider)
    end
end