update config related to folding

1. For python and lua, rely on LSP for folding
2. show fold signs on the right of the number column

after/ftplugin/lua.vim

@@ -3,7 +3,3 @@ set formatoptions-=o
 set formatoptions-=r
 
 nnoremap <buffer><silent> <F9> :luafile %<CR>
-
-" Use nvim-treesitter for folding
-set foldmethod=expr
-set foldexpr=nvim_treesitter#foldexpr()

after/ftplugin/python.vim

@@ -12,7 +12,3 @@ set tabstop=4       " number of visual spaces per TAB
 set softtabstop=4   " number of spaces in tab when editing
 set shiftwidth=4    " number of spaces to use for autoindent
 set expandtab       " expand tab to spaces so that tabs are spaces
-
-" Use nvim-treesitter for folding
-set foldmethod=expr
-set foldexpr=nvim_treesitter#foldexpr()

lua/plugin_specs.lua

@@ -194,9 +194,9 @@ local plugin_specs = {
       require("statuscol").setup {
         relculright = true,
         segments = {
-          { text = { builtin.foldfunc }, click = "v:lua.ScFa" },
           { text = { "%s" }, click = "v:lua.ScSa" },
           { text = { builtin.lnumfunc, " " }, click = "v:lua.ScLa" },
+          { text = { builtin.foldfunc, " " }, condition = {true, builtin.not_empty}, click = "v:lua.ScFa" },
         },
       }
     end,