fix (nvim-lua#1319): gitsigns deprecated functions (nvim-lua#1321)

- This commit change two functions that are marked as deprecated now:
`gitsigns.stage_hunk` and `gitsigns.toggle_deleted`

Author: FuelledByCoffee

lua/kickstart/plugins/gitsigns.lua

@@ -58,6 +58,7 @@ return {
         -- Toggles
         map('n', '<leader>tb', gitsigns.toggle_current_line_blame, { desc = '[T]oggle git show [b]lame line' })
         map('n', '<leader>tD', gitsigns.preview_hunk_inline, { desc = '[T]oggle git show [D]eleted' })
+        map('n', '<leader>tD', gitsigns.preview_hunk_inline, { desc = '[T]oggle git show [D]eleted' })
       end,
     },
   },