refactor(client/progress): don't clear progress on cancel

Sending "progressCancel" to NUI will cause a transition and then
trigger "progressComplete" with a slight delay (~100ms).

Should look better when people queue up progress bars.

resource/interface/client/progress.lua

@@ -147,10 +147,8 @@ local function startProgress(data)
     end
 
     playerState.invBusy = false
-    local cancel = progress == false
-    progress = nil
 
-    if cancel then
+    if progress == false then
         SendNUIMessage({ action = 'progressCancel' })
         return false
     end