vim-patch:9.0.0608: with spelling, deleting a full stop does not update next line

Problem:    With spell checking, deleting a full stop at the end of a line
            does not update SpellCap at the start of the next line.
Solution:   Update the next line when characters have been deleted.  Also when
            using undo.

26f09ea54b

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

src/nvim/undo.c

@@ -120,6 +120,7 @@
 #include "nvim/path.h"
 #include "nvim/pos.h"
 #include "nvim/sha256.h"
+#include "nvim/spell.h"
 #include "nvim/state.h"
 #include "nvim/strings.h"
 #include "nvim/types.h"
@@ -2372,6 +2373,12 @@ static void u_undoredo(int undo, bool do_buf_event)
     }
 
     changed_lines(top + 1, 0, bot, newsize - oldsize, do_buf_event);
+    // When text has been changed, possibly the start of the next line
+    // may have SpellCap that should be removed or it needs to be
+    // displayed.  Schedule the next line for redrawing just in case.
+    if (spell_check_window(curwin) && bot <= curbuf->b_ml.ml_line_count) {
+      redrawWinline(curwin, bot);
+    }
 
     // Set the '[ mark.
     if (top + 1 < curbuf->b_op_start.lnum) {