vim-patch:9.0.2056: no digraph for quadruple prime

Problem:  no digraph for quadruple prime
Solution: add quadruple prime digraph using 4'

closes: vim/vim#13380

47416d1a74

Co-authored-by: Jonathan Wright <quaggy@gmail.com>

src/nvim/digraph.c

@@ -879,6 +879,7 @@ static digr_T digraphdefault[] =
   { '1', '\'', 0x2032 },
   { '2', '\'', 0x2033 },
   { '3', '\'', 0x2034 },
+  { '4', '\'', 0x2057 },
   { '1', '"', 0x2035 },
   { '2', '"', 0x2036 },
   { '3', '"', 0x2037 },