vim-patch:8.1.0022: repeating put from expression register fails

Problem:    Repeating put from expression register fails.
Solution:   Re-evaluate the expression register. (Andy Massimino,
            closes vim/vim#2945)
833093bfb0

src/nvim/getchar.c

@@ -755,6 +755,13 @@ int start_redo(long count, int old_redo)
     if (c >= '1' && c < '9')
       ++c;
     add_char_buff(&readbuf2, c);
+
+    // the expression register should be re-evaluated
+    if (c == '=') {
+      add_char_buff(&readbuf2, CAR);
+      cmd_silent = true;
+    }
+
     c = read_redo(FALSE, old_redo);
   }