Bug(Nui): Following the shutdown handler function, nui focus is set to false

[RockySouthpaw]

Causes issues of where the mouse should be in use but is disabled by the loading screen ending.

Related to: https://github.com/project-error/pe-basicloading/blob/a6a8e1862304e7de6b0d718190fd4992da71c478/client.lua#L3

Current solution is to remove the thread:

local function shutdownHandler()
    SendLoadingScreenMessage(json.encode({fullyLoaded = true}))
    ShutdownLoadingScreenNui(true)
end

Requires additional testing with different pc specs though before making a pull request. Adding it here for issue tracking.

Do note, this wasn't tested with the shutdown export and no convars were set.