vim-patch:8.2.4594: need to write script to a file to be able to source them

Problem:    Need to write script to a file to be able to source them.
Solution:   Make ":source" use lines from the current buffer. (Yegappan
            Lakshmanan et al., closes vim/vim#9967)

36a5b6867b

Most code and test changes are reverted or modified again in patch
8.2.4603, so only port parts that are untouched in patch 8.2.4603.

Co-authored-by: Yegappan Lakshmanan <yegappan@yahoo.com>

src/nvim/ex_cmds.lua

@@ -2533,7 +2533,7 @@ M.cmds = {
   },
   {
     command = 'source',
-    flags = bit.bor(RANGE, DFLALL, WHOLEFOLD, BANG, FILE1, TRLBAR, SBOXOK, CMDWIN, LOCK_OK),
+    flags = bit.bor(RANGE, DFLALL, BANG, FILE1, TRLBAR, SBOXOK, CMDWIN, LOCK_OK),
     addr_type = 'ADDR_LINES',
     func = 'ex_source',
   },