vim-patch:8.2.3467: CursorHoldI event interferes with "CTRL-G U" (#25383)

Problem:    CursorHoldI event interferes with "CTRL-G U". (Naohiro Ono)
Solution:   Restore the flag for "CTRL-G U" after triggering CursorHoldI.
            (closes vim/vim#8937)

5a9357d0bf

Co-authored-by: Bram Moolenaar <Bram@vim.org>

src/nvim/edit.c

@@ -878,6 +878,10 @@ static int insert_handle_key(InsertState *s)
 
   case K_EVENT:       // some event
     state_handle_k_event();
+    // If CTRL-G U was used apply it to the next typed key.
+    if (dont_sync_undo == kTrue) {
+      dont_sync_undo = kNone;
+    }
     goto check_pum;
 
   case K_COMMAND:     // <Cmd>command<CR>