Fix :ga from within REPL

`:ga` Needed to be executed twice if executed from within the REPL
buffer due to a `nvim_buf_delete`/`nvim_win_close` running into a
"Cannot close last window" error.

This replaces the close call with a `modified` change, which serves the
purpose of not blocking an exit if the REPL prompt buffer is modified.

Author: mfussenegger

lua/dap.lua

@@ -1374,7 +1374,7 @@ api.nvim_create_autocmd("ExitPre", {
       ---@diagnostic disable-next-line: redundant-return-value
       return session == nil and next(sessions) == nil
     end)
-    M.repl.close()
+    M.repl._exit()
     if _log then
       _log:close()
     end

lua/dap/repl.lua

@@ -618,4 +618,12 @@ do
 end
 
 
+function M._exit()
+  local buf = repl.buf
+  if buf and vim.bo[buf].modified then
+    vim.bo[buf].modified = false
+  end
+end
+
+
 return M