fix: Reduce memory leaks (#148)

It is not 100% clear that we've gotten ALL the memory leaks, but it
seems much much much better and doesn't look like it's going to die
immediately or as often anymore :)

lua/telescope/sorters.lua

@@ -54,7 +54,7 @@ end
 sorters.Sorter = Sorter
 
 TelescopeCachedTails = TelescopeCachedTails or nil
-do
+if not TelescopeCachedTails then
   local os_sep = util.get_separator()
   local match_string = '[^' .. os_sep .. ']*$'
   TelescopeCachedTails = setmetatable({}, {